Merge pull request #661 from hairyhenderson/git-datasource

New git datasource

68 files changed, 7854 insertions, 0 deletions

diff --git a/vendor/github.com/emirpasic/gods/LICENSE b/vendor/github.com/emirpasic/gods/LICENSE
new file mode 100644
index 00000000..e5e449b6
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/LICENSE
@@ -0,0 +1,41 @@
+Copyright (c) 2015, Emir Pasic
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+-------------------------------------------------------------------------------
+
+AVL Tree:
+
+Copyright (c) 2017 Benjamin Scher Purcell <benjapurcell@gmail.com>
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
diff --git a/vendor/github.com/emirpasic/gods/containers/containers.go b/vendor/github.com/emirpasic/gods/containers/containers.go
new file mode 100644
index 00000000..c35ab36d
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/containers/containers.go
@@ -0,0 +1,35 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package containers provides core interfaces and functions for data structures.
+//
+// Container is the base interface for all data structures to implement.
+//
+// Iterators provide stateful iterators.
+//
+// Enumerable provides Ruby inspired (each, select, map, find, any?, etc.) container functions.
+//
+// Serialization provides serializers (marshalers) and deserializers (unmarshalers).
+package containers
+
+import "github.com/emirpasic/gods/utils"
+
+// Container is base interface that all data structures implement.
+type Container interface {
+	Empty() bool
+	Size() int
+	Clear()
+	Values() []interface{}
+}
+
+// GetSortedValues returns sorted container's elements with respect to the passed comparator.
+// Does not effect the ordering of elements within the container.
+func GetSortedValues(container Container, comparator utils.Comparator) []interface{} {
+	values := container.Values()
+	if len(values) < 2 {
+		return values
+	}
+	utils.Sort(values, comparator)
+	return values
+}
diff --git a/vendor/github.com/emirpasic/gods/containers/enumerable.go b/vendor/github.com/emirpasic/gods/containers/enumerable.go
new file mode 100644
index 00000000..ac48b545
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/containers/enumerable.go
@@ -0,0 +1,61 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package containers
+
+// EnumerableWithIndex provides functions for ordered containers whose values can be fetched by an index.
+type EnumerableWithIndex interface {
+	// Each calls the given function once for each element, passing that element's index and value.
+	Each(func(index int, value interface{}))
+
+	// Map invokes the given function once for each element and returns a
+	// container containing the values returned by the given function.
+	// TODO would appreciate help on how to enforce this in containers (don't want to type assert when chaining)
+	// Map(func(index int, value interface{}) interface{}) Container
+
+	// Select returns a new container containing all elements for which the given function returns a true value.
+	// TODO need help on how to enforce this in containers (don't want to type assert when chaining)
+	// Select(func(index int, value interface{}) bool) Container
+
+	// Any passes each element of the container to the given function and
+	// returns true if the function ever returns true for any element.
+	Any(func(index int, value interface{}) bool) bool
+
+	// All passes each element of the container to the given function and
+	// returns true if the function returns true for all elements.
+	All(func(index int, value interface{}) bool) bool
+
+	// Find passes each element of the container to the given function and returns
+	// the first (index,value) for which the function is true or -1,nil otherwise
+	// if no element matches the criteria.
+	Find(func(index int, value interface{}) bool) (int, interface{})
+}
+
+// EnumerableWithKey provides functions for ordered containers whose values whose elements are key/value pairs.
+type EnumerableWithKey interface {
+	// Each calls the given function once for each element, passing that element's key and value.
+	Each(func(key interface{}, value interface{}))
+
+	// Map invokes the given function once for each element and returns a container
+	// containing the values returned by the given function as key/value pairs.
+	// TODO need help on how to enforce this in containers (don't want to type assert when chaining)
+	// Map(func(key interface{}, value interface{}) (interface{}, interface{})) Container
+
+	// Select returns a new container containing all elements for which the given function returns a true value.
+	// TODO need help on how to enforce this in containers (don't want to type assert when chaining)
+	// Select(func(key interface{}, value interface{}) bool) Container
+
+	// Any passes each element of the container to the given function and
+	// returns true if the function ever returns true for any element.
+	Any(func(key interface{}, value interface{}) bool) bool
+
+	// All passes each element of the container to the given function and
+	// returns true if the function returns true for all elements.
+	All(func(key interface{}, value interface{}) bool) bool
+
+	// Find passes each element of the container to the given function and returns
+	// the first (key,value) for which the function is true or nil,nil otherwise if no element
+	// matches the criteria.
+	Find(func(key interface{}, value interface{}) bool) (interface{}, interface{})
+}
diff --git a/vendor/github.com/emirpasic/gods/containers/iterator.go b/vendor/github.com/emirpasic/gods/containers/iterator.go
new file mode 100644
index 00000000..f1a52a36
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/containers/iterator.go
@@ -0,0 +1,109 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package containers
+
+// IteratorWithIndex is stateful iterator for ordered containers whose values can be fetched by an index.
+type IteratorWithIndex interface {
+	// Next moves the iterator to the next element and returns true if there was a next element in the container.
+	// If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
+	// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
+	// Modifies the state of the iterator.
+	Next() bool
+
+	// Value returns the current element's value.
+	// Does not modify the state of the iterator.
+	Value() interface{}
+
+	// Index returns the current element's index.
+	// Does not modify the state of the iterator.
+	Index() int
+
+	// Begin resets the iterator to its initial state (one-before-first)
+	// Call Next() to fetch the first element if any.
+	Begin()
+
+	// First moves the iterator to the first element and returns true if there was a first element in the container.
+	// If First() returns true, then first element's index and value can be retrieved by Index() and Value().
+	// Modifies the state of the iterator.
+	First() bool
+}
+
+// IteratorWithKey is a stateful iterator for ordered containers whose elements are key value pairs.
+type IteratorWithKey interface {
+	// Next moves the iterator to the next element and returns true if there was a next element in the container.
+	// If Next() returns true, then next element's key and value can be retrieved by Key() and Value().
+	// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
+	// Modifies the state of the iterator.
+	Next() bool
+
+	// Value returns the current element's value.
+	// Does not modify the state of the iterator.
+	Value() interface{}
+
+	// Key returns the current element's key.
+	// Does not modify the state of the iterator.
+	Key() interface{}
+
+	// Begin resets the iterator to its initial state (one-before-first)
+	// Call Next() to fetch the first element if any.
+	Begin()
+
+	// First moves the iterator to the first element and returns true if there was a first element in the container.
+	// If First() returns true, then first element's key and value can be retrieved by Key() and Value().
+	// Modifies the state of the iterator.
+	First() bool
+}
+
+// ReverseIteratorWithIndex is stateful iterator for ordered containers whose values can be fetched by an index.
+//
+// Essentially it is the same as IteratorWithIndex, but provides additional:
+//
+// Prev() function to enable traversal in reverse
+//
+// Last() function to move the iterator to the last element.
+//
+// End() function to move the iterator past the last element (one-past-the-end).
+type ReverseIteratorWithIndex interface {
+	// Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
+	// If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
+	// Modifies the state of the iterator.
+	Prev() bool
+
+	// End moves the iterator past the last element (one-past-the-end).
+	// Call Prev() to fetch the last element if any.
+	End()
+
+	// Last moves the iterator to the last element and returns true if there was a last element in the container.
+	// If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
+	// Modifies the state of the iterator.
+	Last() bool
+
+	IteratorWithIndex
+}
+
+// ReverseIteratorWithKey is a stateful iterator for ordered containers whose elements are key value pairs.
+//
+// Essentially it is the same as IteratorWithKey, but provides additional:
+//
+// Prev() function to enable traversal in reverse
+//
+// Last() function to move the iterator to the last element.
+type ReverseIteratorWithKey interface {
+	// Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
+	// If Prev() returns true, then previous element's key and value can be retrieved by Key() and Value().
+	// Modifies the state of the iterator.
+	Prev() bool
+
+	// End moves the iterator past the last element (one-past-the-end).
+	// Call Prev() to fetch the last element if any.
+	End()
+
+	// Last moves the iterator to the last element and returns true if there was a last element in the container.
+	// If Last() returns true, then last element's key and value can be retrieved by Key() and Value().
+	// Modifies the state of the iterator.
+	Last() bool
+
+	IteratorWithKey
+}
diff --git a/vendor/github.com/emirpasic/gods/containers/serialization.go b/vendor/github.com/emirpasic/gods/containers/serialization.go
new file mode 100644
index 00000000..d7c90c83
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/containers/serialization.go
@@ -0,0 +1,17 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package containers
+
+// JSONSerializer provides JSON serialization
+type JSONSerializer interface {
+	// ToJSON outputs the JSON representation of containers's elements.
+	ToJSON() ([]byte, error)
+}
+
+// JSONDeserializer provides JSON deserialization
+type JSONDeserializer interface {
+	// FromJSON populates containers's elements from the input JSON representation.
+	FromJSON([]byte) error
+}
diff --git a/vendor/github.com/emirpasic/gods/lists/arraylist/arraylist.go b/vendor/github.com/emirpasic/gods/lists/arraylist/arraylist.go
new file mode 100644
index 00000000..bfedac9e
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/lists/arraylist/arraylist.go
@@ -0,0 +1,228 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package arraylist implements the array list.
+//
+// Structure is not thread safe.
+//
+// Reference: https://en.wikipedia.org/wiki/List_%28abstract_data_type%29
+package arraylist
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/emirpasic/gods/lists"
+	"github.com/emirpasic/gods/utils"
+)
+
+func assertListImplementation() {
+	var _ lists.List = (*List)(nil)
+}
+
+// List holds the elements in a slice
+type List struct {
+	elements []interface{}
+	size     int
+}
+
+const (
+	growthFactor = float32(2.0)  // growth by 100%
+	shrinkFactor = float32(0.25) // shrink when size is 25% of capacity (0 means never shrink)
+)
+
+// New instantiates a new list and adds the passed values, if any, to the list
+func New(values ...interface{}) *List {
+	list := &List{}
+	if len(values) > 0 {
+		list.Add(values...)
+	}
+	return list
+}
+
+// Add appends a value at the end of the list
+func (list *List) Add(values ...interface{}) {
+	list.growBy(len(values))
+	for _, value := range values {
+		list.elements[list.size] = value
+		list.size++
+	}
+}
+
+// Get returns the element at index.
+// Second return parameter is true if index is within bounds of the array and array is not empty, otherwise false.
+func (list *List) Get(index int) (interface{}, bool) {
+
+	if !list.withinRange(index) {
+		return nil, false
+	}
+
+	return list.elements[index], true
+}
+
+// Remove removes the element at the given index from the list.
+func (list *List) Remove(index int) {
+
+	if !list.withinRange(index) {
+		return
+	}
+
+	list.elements[index] = nil                                    // cleanup reference
+	copy(list.elements[index:], list.elements[index+1:list.size]) // shift to the left by one (slow operation, need ways to optimize this)
+	list.size--
+
+	list.shrink()
+}
+
+// Contains checks if elements (one or more) are present in the set.
+// All elements have to be present in the set for the method to return true.
+// Performance time complexity of n^2.
+// Returns true if no arguments are passed at all, i.e. set is always super-set of empty set.
+func (list *List) Contains(values ...interface{}) bool {
+
+	for _, searchValue := range values {
+		found := false
+		for _, element := range list.elements {
+			if element == searchValue {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+	return true
+}
+
+// Values returns all elements in the list.
+func (list *List) Values() []interface{} {
+	newElements := make([]interface{}, list.size, list.size)
+	copy(newElements, list.elements[:list.size])
+	return newElements
+}
+
+//IndexOf returns index of provided element
+func (list *List) IndexOf(value interface{}) int {
+	if list.size == 0 {
+		return -1
+	}
+	for index, element := range list.elements {
+		if element == value {
+			return index
+		}
+	}
+	return -1
+}
+
+// Empty returns true if list does not contain any elements.
+func (list *List) Empty() bool {
+	return list.size == 0
+}
+
+// Size returns number of elements within the list.
+func (list *List) Size() int {
+	return list.size
+}
+
+// Clear removes all elements from the list.
+func (list *List) Clear() {
+	list.size = 0
+	list.elements = []interface{}{}
+}
+
+// Sort sorts values (in-place) using.
+func (list *List) Sort(comparator utils.Comparator) {
+	if len(list.elements) < 2 {
+		return
+	}
+	utils.Sort(list.elements[:list.size], comparator)
+}
+
+// Swap swaps the two values at the specified positions.
+func (list *List) Swap(i, j int) {
+	if list.withinRange(i) && list.withinRange(j) {
+		list.elements[i], list.elements[j] = list.elements[j], list.elements[i]
+	}
+}
+
+// Insert inserts values at specified index position shifting the value at that position (if any) and any subsequent elements to the right.
+// Does not do anything if position is negative or bigger than list's size
+// Note: position equal to list's size is valid, i.e. append.
+func (list *List) Insert(index int, values ...interface{}) {
+
+	if !list.withinRange(index) {
+		// Append
+		if index == list.size {
+			list.Add(values...)
+		}
+		return
+	}
+
+	l := len(values)
+	list.growBy(l)
+	list.size += l
+	copy(list.elements[index+l:], list.elements[index:list.size-l])
+	copy(list.elements[index:], values)
+}
+
+// Set the value at specified index
+// Does not do anything if position is negative or bigger than list's size
+// Note: position equal to list's size is valid, i.e. append.
+func (list *List) Set(index int, value interface{}) {
+
+	if !list.withinRange(index) {
+		// Append
+		if index == list.size {
+			list.Add(value)
+		}
+		return
+	}
+
+	list.elements[index] = value
+}
+
+// String returns a string representation of container
+func (list *List) String() string {
+	str := "ArrayList\n"
+	values := []string{}
+	for _, value := range list.elements[:list.size] {
+		values = append(values, fmt.Sprintf("%v", value))
+	}
+	str += strings.Join(values, ", ")
+	return str
+}
+
+// Check that the index is within bounds of the list
+func (list *List) withinRange(index int) bool {
+	return index >= 0 && index < list.size
+}
+
+func (list *List) resize(cap int) {
+	newElements := make([]interface{}, cap, cap)
+	copy(newElements, list.elements)
+	list.elements = newElements
+}
+
+// Expand the array if necessary, i.e. capacity will be reached if we add n elements
+func (list *List) growBy(n int) {
+	// When capacity is reached, grow by a factor of growthFactor and add number of elements
+	currentCapacity := cap(list.elements)
+	if list.size+n >= currentCapacity {
+		newCapacity := int(growthFactor * float32(currentCapacity+n))
+		list.resize(newCapacity)
+	}
+}
+
+// Shrink the array if necessary, i.e. when size is shrinkFactor percent of current capacity
+func (list *List) shrink() {
+	if shrinkFactor == 0.0 {
+		return
+	}
+	// Shrink when size is at shrinkFactor * capacity
+	currentCapacity := cap(list.elements)
+	if list.size <= int(float32(currentCapacity)*shrinkFactor) {
+		list.resize(list.size)
+	}
+}
diff --git a/vendor/github.com/emirpasic/gods/lists/arraylist/enumerable.go b/vendor/github.com/emirpasic/gods/lists/arraylist/enumerable.go
new file mode 100644
index 00000000..b3a87388
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/lists/arraylist/enumerable.go
@@ -0,0 +1,79 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package arraylist
+
+import "github.com/emirpasic/gods/containers"
+
+func assertEnumerableImplementation() {
+	var _ containers.EnumerableWithIndex = (*List)(nil)
+}
+
+// Each calls the given function once for each element, passing that element's index and value.
+func (list *List) Each(f func(index int, value interface{})) {
+	iterator := list.Iterator()
+	for iterator.Next() {
+		f(iterator.Index(), iterator.Value())
+	}
+}
+
+// Map invokes the given function once for each element and returns a
+// container containing the values returned by the given function.
+func (list *List) Map(f func(index int, value interface{}) interface{}) *List {
+	newList := &List{}
+	iterator := list.Iterator()
+	for iterator.Next() {
+		newList.Add(f(iterator.Index(), iterator.Value()))
+	}
+	return newList
+}
+
+// Select returns a new container containing all elements for which the given function returns a true value.
+func (list *List) Select(f func(index int, value interface{}) bool) *List {
+	newList := &List{}
+	iterator := list.Iterator()
+	for iterator.Next() {
+		if f(iterator.Index(), iterator.Value()) {
+			newList.Add(iterator.Value())
+		}
+	}
+	return newList
+}
+
+// Any passes each element of the collection to the given function and
+// returns true if the function ever returns true for any element.
+func (list *List) Any(f func(index int, value interface{}) bool) bool {
+	iterator := list.Iterator()
+	for iterator.Next() {
+		if f(iterator.Index(), iterator.Value()) {
+			return true
+		}
+	}
+	return false
+}
+
+// All passes each element of the collection to the given function and
+// returns true if the function returns true for all elements.
+func (list *List) All(f func(index int, value interface{}) bool) bool {
+	iterator := list.Iterator()
+	for iterator.Next() {
+		if !f(iterator.Index(), iterator.Value()) {
+			return false
+		}
+	}
+	return true
+}
+
+// Find passes each element of the container to the given function and returns
+// the first (index,value) for which the function is true or -1,nil otherwise
+// if no element matches the criteria.
+func (list *List) Find(f func(index int, value interface{}) bool) (int, interface{}) {
+	iterator := list.Iterator()
+	for iterator.Next() {
+		if f(iterator.Index(), iterator.Value()) {
+			return iterator.Index(), iterator.Value()
+		}
+	}
+	return -1, nil
+}
diff --git a/vendor/github.com/emirpasic/gods/lists/arraylist/iterator.go b/vendor/github.com/emirpasic/gods/lists/arraylist/iterator.go
new file mode 100644
index 00000000..38a93f3a
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/lists/arraylist/iterator.go
@@ -0,0 +1,83 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package arraylist
+
+import "github.com/emirpasic/gods/containers"
+
+func assertIteratorImplementation() {
+	var _ containers.ReverseIteratorWithIndex = (*Iterator)(nil)
+}
+
+// Iterator holding the iterator's state
+type Iterator struct {
+	list  *List
+	index int
+}
+
+// Iterator returns a stateful iterator whose values can be fetched by an index.
+func (list *List) Iterator() Iterator {
+	return Iterator{list: list, index: -1}
+}
+
+// Next moves the iterator to the next element and returns true if there was a next element in the container.
+// If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
+// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
+// Modifies the state of the iterator.
+func (iterator *Iterator) Next() bool {
+	if iterator.index < iterator.list.size {
+		iterator.index++
+	}
+	return iterator.list.withinRange(iterator.index)
+}
+
+// Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
+// If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
+// Modifies the state of the iterator.
+func (iterator *Iterator) Prev() bool {
+	if iterator.index >= 0 {
+		iterator.index--
+	}
+	return iterator.list.withinRange(iterator.index)
+}
+
+// Value returns the current element's value.
+// Does not modify the state of the iterator.
+func (iterator *Iterator) Value() interface{} {
+	return iterator.list.elements[iterator.index]
+}
+
+// Index returns the current element's index.
+// Does not modify the state of the iterator.
+func (iterator *Iterator) Index() int {
+	return iterator.index
+}
+
+// Begin resets the iterator to its initial state (one-before-first)
+// Call Next() to fetch the first element if any.
+func (iterator *Iterator) Begin() {
+	iterator.index = -1
+}
+
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.index = iterator.list.size
+}
+
+// First moves the iterator to the first element and returns true if there was a first element in the container.
+// If First() returns true, then first element's index and value can be retrieved by Index() and Value().
+// Modifies the state of the iterator.
+func (iterator *Iterator) First() bool {
+	iterator.Begin()
+	return iterator.Next()
+}
+
+// Last moves the iterator to the last element and returns true if there was a last element in the container.
+// If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
+// Modifies the state of the iterator.
+func (iterator *Iterator) Last() bool {
+	iterator.End()
+	return iterator.Prev()
+}
diff --git a/vendor/github.com/emirpasic/gods/lists/arraylist/serialization.go b/vendor/github.com/emirpasic/gods/lists/arraylist/serialization.go
new file mode 100644
index 00000000..2f283fb9
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/lists/arraylist/serialization.go
@@ -0,0 +1,29 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package arraylist
+
+import (
+	"encoding/json"
+	"github.com/emirpasic/gods/containers"
+)
+
+func assertSerializationImplementation() {
+	var _ containers.JSONSerializer = (*List)(nil)
+	var _ containers.JSONDeserializer = (*List)(nil)
+}
+
+// ToJSON outputs the JSON representation of list's elements.
+func (list *List) ToJSON() ([]byte, error) {
+	return json.Marshal(list.elements[:list.size])
+}
+
+// FromJSON populates list's elements from the input JSON representation.
+func (list *List) FromJSON(data []byte) error {
+	err := json.Unmarshal(data, &list.elements)
+	if err == nil {
+		list.size = len(list.elements)
+	}
+	return err
+}
diff --git a/vendor/github.com/emirpasic/gods/lists/lists.go b/vendor/github.com/emirpasic/gods/lists/lists.go
new file mode 100644
index 00000000..1f6bb08e
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/lists/lists.go
@@ -0,0 +1,33 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package lists provides an abstract List interface.
+//
+// In computer science, a list or sequence is an abstract data type that represents an ordered sequence of values, where the same value may occur more than once. An instance of a list is a computer representation of the mathematical concept of a finite sequence; the (potentially) infinite analog of a list is a stream.  Lists are a basic example of containers, as they contain other values. If the same value occurs multiple times, each occurrence is considered a distinct item.
+//
+// Reference: https://en.wikipedia.org/wiki/List_%28abstract_data_type%29
+package lists
+
+import (
+	"github.com/emirpasic/gods/containers"
+	"github.com/emirpasic/gods/utils"
+)
+
+// List interface that all lists implement
+type List interface {
+	Get(index int) (interface{}, bool)
+	Remove(index int)
+	Add(values ...interface{})
+	Contains(values ...interface{}) bool
+	Sort(comparator utils.Comparator)
+	Swap(index1, index2 int)
+	Insert(index int, values ...interface{})
+	Set(index int, value interface{})
+
+	containers.Container
+	// Empty() bool
+	// Size() int
+	// Clear()
+	// Values() []interface{}
+}
diff --git a/vendor/github.com/emirpasic/gods/trees/binaryheap/binaryheap.go b/vendor/github.com/emirpasic/gods/trees/binaryheap/binaryheap.go
new file mode 100644
index 00000000..70b28cf5
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/trees/binaryheap/binaryheap.go
@@ -0,0 +1,163 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package binaryheap implements a binary heap backed by array list.
+//
+// Comparator defines this heap as either min or max heap.
+//
+// Structure is not thread safe.
+//
+// References: http://en.wikipedia.org/wiki/Binary_heap
+package binaryheap
+
+import (
+	"fmt"
+	"github.com/emirpasic/gods/lists/arraylist"
+	"github.com/emirpasic/gods/trees"
+	"github.com/emirpasic/gods/utils"
+	"strings"
+)
+
+func assertTreeImplementation() {
+	var _ trees.Tree = (*Heap)(nil)
+}
+
+// Heap holds elements in an array-list
+type Heap struct {
+	list       *arraylist.List
+	Comparator utils.Comparator
+}
+
+// NewWith instantiates a new empty heap tree with the custom comparator.
+func NewWith(comparator utils.Comparator) *Heap {
+	return &Heap{list: arraylist.New(), Comparator: comparator}
+}
+
+// NewWithIntComparator instantiates a new empty heap with the IntComparator, i.e. elements are of type int.
+func NewWithIntComparator() *Heap {
+	return &Heap{list: arraylist.New(), Comparator: utils.IntComparator}
+}
+
+// NewWithStringComparator instantiates a new empty heap with the StringComparator, i.e. elements are of type string.
+func NewWithStringComparator() *Heap {
+	return &Heap{list: arraylist.New(), Comparator: utils.StringComparator}
+}
+
+// Push adds a value onto the heap and bubbles it up accordingly.
+func (heap *Heap) Push(values ...interface{}) {
+	if len(values) == 1 {
+		heap.list.Add(values[0])
+		heap.bubbleUp()
+	} else {
+		// Reference: https://en.wikipedia.org/wiki/Binary_heap#Building_a_heap
+		for _, value := range values {
+			heap.list.Add(value)
+		}
+		size := heap.list.Size()/2 + 1
+		for i := size; i >= 0; i-- {
+			heap.bubbleDownIndex(i)
+		}
+	}
+}
+
+// Pop removes top element on heap and returns it, or nil if heap is empty.
+// Second return parameter is true, unless the heap was empty and there was nothing to pop.
+func (heap *Heap) Pop() (value interface{}, ok bool) {
+	value, ok = heap.list.Get(0)
+	if !ok {
+		return
+	}
+	lastIndex := heap.list.Size() - 1
+	heap.list.Swap(0, lastIndex)
+	heap.list.Remove(lastIndex)
+	heap.bubbleDown()
+	return
+}
+
+// Peek returns top element on the heap without removing it, or nil if heap is empty.
+// Second return parameter is true, unless the heap was empty and there was nothing to peek.
+func (heap *Heap) Peek() (value interface{}, ok bool) {
+	return heap.list.Get(0)
+}
+
+// Empty returns true if heap does not contain any elements.
+func (heap *Heap) Empty() bool {
+	return heap.list.Empty()
+}
+
+// Size returns number of elements within the heap.
+func (heap *Heap) Size() int {
+	return heap.list.Size()
+}
+
+// Clear removes all elements from the heap.
+func (heap *Heap) Clear() {
+	heap.list.Clear()
+}
+
+// Values returns all elements in the heap.
+func (heap *Heap) Values() []interface{} {
+	return heap.list.Values()
+}
+
+// String returns a string representation of container
+func (heap *Heap) String() string {
+	str := "BinaryHeap\n"
+	values := []string{}
+	for _, value := range heap.list.Values() {
+		values = append(values, fmt.Sprintf("%v", value))
+	}
+	str += strings.Join(values, ", ")
+	return str
+}
+
+// Performs the "bubble down" operation. This is to place the element that is at the root
+// of the heap in its correct place so that the heap maintains the min/max-heap order property.
+func (heap *Heap) bubbleDown() {
+	heap.bubbleDownIndex(0)
+}
+
+// Performs the "bubble down" operation. This is to place the element that is at the index
+// of the heap in its correct place so that the heap maintains the min/max-heap order property.
+func (heap *Heap) bubbleDownIndex(index int) {
+	size := heap.list.Size()
+	for leftIndex := index<<1 + 1; leftIndex < size; leftIndex = index<<1 + 1 {
+		rightIndex := index<<1 + 2
+		smallerIndex := leftIndex
+		leftValue, _ := heap.list.Get(leftIndex)
+		rightValue, _ := heap.list.Get(rightIndex)
+		if rightIndex < size && heap.Comparator(leftValue, rightValue) > 0 {
+			smallerIndex = rightIndex
+		}
+		indexValue, _ := heap.list.Get(index)
+		smallerValue, _ := heap.list.Get(smallerIndex)
+		if heap.Comparator(indexValue, smallerValue) > 0 {
+			heap.list.Swap(index, smallerIndex)
+		} else {
+			break
+		}
+		index = smallerIndex
+	}
+}
+
+// Performs the "bubble up" operation. This is to place a newly inserted
+// element (i.e. last element in the list) in its correct place so that
+// the heap maintains the min/max-heap order property.
+func (heap *Heap) bubbleUp() {
+	index := heap.list.Size() - 1
+	for parentIndex := (index - 1) >> 1; index > 0; parentIndex = (index - 1) >> 1 {
+		indexValue, _ := heap.list.Get(index)
+		parentValue, _ := heap.list.Get(parentIndex)
+		if heap.Comparator(parentValue, indexValue) <= 0 {
+			break
+		}
+		heap.list.Swap(index, parentIndex)
+		index = parentIndex
+	}
+}
+
+// Check that the index is within bounds of the list
+func (heap *Heap) withinRange(index int) bool {
+	return index >= 0 && index < heap.list.Size()
+}
diff --git a/vendor/github.com/emirpasic/gods/trees/binaryheap/iterator.go b/vendor/github.com/emirpasic/gods/trees/binaryheap/iterator.go
new file mode 100644
index 00000000..beeb8d70
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/trees/binaryheap/iterator.go
@@ -0,0 +1,84 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package binaryheap
+
+import "github.com/emirpasic/gods/containers"
+
+func assertIteratorImplementation() {
+	var _ containers.ReverseIteratorWithIndex = (*Iterator)(nil)
+}
+
+// Iterator returns a stateful iterator whose values can be fetched by an index.
+type Iterator struct {
+	heap  *Heap
+	index int
+}
+
+// Iterator returns a stateful iterator whose values can be fetched by an index.
+func (heap *Heap) Iterator() Iterator {
+	return Iterator{heap: heap, index: -1}
+}
+
+// Next moves the iterator to the next element and returns true if there was a next element in the container.
+// If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
+// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
+// Modifies the state of the iterator.
+func (iterator *Iterator) Next() bool {
+	if iterator.index < iterator.heap.Size() {
+		iterator.index++
+	}
+	return iterator.heap.withinRange(iterator.index)
+}
+
+// Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
+// If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
+// Modifies the state of the iterator.
+func (iterator *Iterator) Prev() bool {
+	if iterator.index >= 0 {
+		iterator.index--
+	}
+	return iterator.heap.withinRange(iterator.index)
+}
+
+// Value returns the current element's value.
+// Does not modify the state of the iterator.
+func (iterator *Iterator) Value() interface{} {
+	value, _ := iterator.heap.list.Get(iterator.index)
+	return value
+}
+
+// Index returns the current element's index.
+// Does not modify the state of the iterator.
+func (iterator *Iterator) Index() int {
+	return iterator.index
+}
+
+// Begin resets the iterator to its initial state (one-before-first)
+// Call Next() to fetch the first element if any.
+func (iterator *Iterator) Begin() {
+	iterator.index = -1
+}
+
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.index = iterator.heap.Size()
+}
+
+// First moves the iterator to the first element and returns true if there was a first element in the container.
+// If First() returns true, then first element's index and value can be retrieved by Index() and Value().
+// Modifies the state of the iterator.
+func (iterator *Iterator) First() bool {
+	iterator.Begin()
+	return iterator.Next()
+}
+
+// Last moves the iterator to the last element and returns true if there was a last element in the container.
+// If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
+// Modifies the state of the iterator.
+func (iterator *Iterator) Last() bool {
+	iterator.End()
+	return iterator.Prev()
+}
diff --git a/vendor/github.com/emirpasic/gods/trees/binaryheap/serialization.go b/vendor/github.com/emirpasic/gods/trees/binaryheap/serialization.go
new file mode 100644
index 00000000..00d0c771
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/trees/binaryheap/serialization.go
@@ -0,0 +1,22 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package binaryheap
+
+import "github.com/emirpasic/gods/containers"
+
+func assertSerializationImplementation() {
+	var _ containers.JSONSerializer = (*Heap)(nil)
+	var _ containers.JSONDeserializer = (*Heap)(nil)
+}
+
+// ToJSON outputs the JSON representation of the heap.
+func (heap *Heap) ToJSON() ([]byte, error) {
+	return heap.list.ToJSON()
+}
+
+// FromJSON populates the heap from the input JSON representation.
+func (heap *Heap) FromJSON(data []byte) error {
+	return heap.list.FromJSON(data)
+}
diff --git a/vendor/github.com/emirpasic/gods/trees/trees.go b/vendor/github.com/emirpasic/gods/trees/trees.go
new file mode 100644
index 00000000..a5a7427d
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/trees/trees.go
@@ -0,0 +1,21 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package trees provides an abstract Tree interface.
+//
+// In computer science, a tree is a widely used abstract data type (ADT) or data structure implementing this ADT that simulates a hierarchical tree structure, with a root value and subtrees of children with a parent node, represented as a set of linked nodes.
+//
+// Reference: https://en.wikipedia.org/wiki/Tree_%28data_structure%29
+package trees
+
+import "github.com/emirpasic/gods/containers"
+
+// Tree interface that all trees implement
+type Tree interface {
+	containers.Container
+	// Empty() bool
+	// Size() int
+	// Clear()
+	// Values() []interface{}
+}
diff --git a/vendor/github.com/emirpasic/gods/utils/comparator.go b/vendor/github.com/emirpasic/gods/utils/comparator.go
new file mode 100644
index 00000000..6a9afbf3
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/utils/comparator.go
@@ -0,0 +1,251 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package utils
+
+import "time"
+
+// Comparator will make type assertion (see IntComparator for example),
+// which will panic if a or b are not of the asserted type.
+//
+// Should return a number:
+//    negative , if a < b
+//    zero     , if a == b
+//    positive , if a > b
+type Comparator func(a, b interface{}) int
+
+// StringComparator provides a fast comparison on strings
+func StringComparator(a, b interface{}) int {
+	s1 := a.(string)
+	s2 := b.(string)
+	min := len(s2)
+	if len(s1) < len(s2) {
+		min = len(s1)
+	}
+	diff := 0
+	for i := 0; i < min && diff == 0; i++ {
+		diff = int(s1[i]) - int(s2[i])
+	}
+	if diff == 0 {
+		diff = len(s1) - len(s2)
+	}
+	if diff < 0 {
+		return -1
+	}
+	if diff > 0 {
+		return 1
+	}
+	return 0
+}
+
+// IntComparator provides a basic comparison on int
+func IntComparator(a, b interface{}) int {
+	aAsserted := a.(int)
+	bAsserted := b.(int)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// Int8Comparator provides a basic comparison on int8
+func Int8Comparator(a, b interface{}) int {
+	aAsserted := a.(int8)
+	bAsserted := b.(int8)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// Int16Comparator provides a basic comparison on int16
+func Int16Comparator(a, b interface{}) int {
+	aAsserted := a.(int16)
+	bAsserted := b.(int16)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// Int32Comparator provides a basic comparison on int32
+func Int32Comparator(a, b interface{}) int {
+	aAsserted := a.(int32)
+	bAsserted := b.(int32)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// Int64Comparator provides a basic comparison on int64
+func Int64Comparator(a, b interface{}) int {
+	aAsserted := a.(int64)
+	bAsserted := b.(int64)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// UIntComparator provides a basic comparison on uint
+func UIntComparator(a, b interface{}) int {
+	aAsserted := a.(uint)
+	bAsserted := b.(uint)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// UInt8Comparator provides a basic comparison on uint8
+func UInt8Comparator(a, b interface{}) int {
+	aAsserted := a.(uint8)
+	bAsserted := b.(uint8)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// UInt16Comparator provides a basic comparison on uint16
+func UInt16Comparator(a, b interface{}) int {
+	aAsserted := a.(uint16)
+	bAsserted := b.(uint16)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// UInt32Comparator provides a basic comparison on uint32
+func UInt32Comparator(a, b interface{}) int {
+	aAsserted := a.(uint32)
+	bAsserted := b.(uint32)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// UInt64Comparator provides a basic comparison on uint64
+func UInt64Comparator(a, b interface{}) int {
+	aAsserted := a.(uint64)
+	bAsserted := b.(uint64)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// Float32Comparator provides a basic comparison on float32
+func Float32Comparator(a, b interface{}) int {
+	aAsserted := a.(float32)
+	bAsserted := b.(float32)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// Float64Comparator provides a basic comparison on float64
+func Float64Comparator(a, b interface{}) int {
+	aAsserted := a.(float64)
+	bAsserted := b.(float64)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// ByteComparator provides a basic comparison on byte
+func ByteComparator(a, b interface{}) int {
+	aAsserted := a.(byte)
+	bAsserted := b.(byte)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// RuneComparator provides a basic comparison on rune
+func RuneComparator(a, b interface{}) int {
+	aAsserted := a.(rune)
+	bAsserted := b.(rune)
+	switch {
+	case aAsserted > bAsserted:
+		return 1
+	case aAsserted < bAsserted:
+		return -1
+	default:
+		return 0
+	}
+}
+
+// TimeComparator provides a basic comparison on time.Time
+func TimeComparator(a, b interface{}) int {
+	aAsserted := a.(time.Time)
+	bAsserted := b.(time.Time)
+
+	switch {
+	case aAsserted.After(bAsserted):
+		return 1
+	case aAsserted.Before(bAsserted):
+		return -1
+	default:
+		return 0
+	}
+}
diff --git a/vendor/github.com/emirpasic/gods/utils/sort.go b/vendor/github.com/emirpasic/gods/utils/sort.go
new file mode 100644
index 00000000..79ced1f5
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/utils/sort.go
@@ -0,0 +1,29 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package utils
+
+import "sort"
+
+// Sort sorts values (in-place) with respect to the given comparator.
+//
+// Uses Go's sort (hybrid of quicksort for large and then insertion sort for smaller slices).
+func Sort(values []interface{}, comparator Comparator) {
+	sort.Sort(sortable{values, comparator})
+}
+
+type sortable struct {
+	values     []interface{}
+	comparator Comparator
+}
+
+func (s sortable) Len() int {
+	return len(s.values)
+}
+func (s sortable) Swap(i, j int) {
+	s.values[i], s.values[j] = s.values[j], s.values[i]
+}
+func (s sortable) Less(i, j int) bool {
+	return s.comparator(s.values[i], s.values[j]) < 0
+}
diff --git a/vendor/github.com/emirpasic/gods/utils/utils.go b/vendor/github.com/emirpasic/gods/utils/utils.go
new file mode 100644
index 00000000..1ad49cbc
--- /dev/null
+++ b/vendor/github.com/emirpasic/gods/utils/utils.go
@@ -0,0 +1,47 @@
+// Copyright (c) 2015, Emir Pasic. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package utils provides common utility functions.
+//
+// Provided functionalities:
+// - sorting
+// - comparators
+package utils
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// ToString converts a value to string.
+func ToString(value interface{}) string {
+	switch value.(type) {
+	case string:
+		return value.(string)
+	case int8:
+		return strconv.FormatInt(int64(value.(int8)), 10)
+	case int16:
+		return strconv.FormatInt(int64(value.(int16)), 10)
+	case int32:
+		return strconv.FormatInt(int64(value.(int32)), 10)
+	case int64:
+		return strconv.FormatInt(int64(value.(int64)), 10)
+	case uint8:
+		return strconv.FormatUint(uint64(value.(uint8)), 10)
+	case uint16:
+		return strconv.FormatUint(uint64(value.(uint16)), 10)
+	case uint32:
+		return strconv.FormatUint(uint64(value.(uint32)), 10)
+	case uint64:
+		return strconv.FormatUint(uint64(value.(uint64)), 10)
+	case float32:
+		return strconv.FormatFloat(float64(value.(float32)), 'g', -1, 64)
+	case float64:
+		return strconv.FormatFloat(float64(value.(float64)), 'g', -1, 64)
+	case bool:
+		return strconv.FormatBool(value.(bool))
+	default:
+		return fmt.Sprintf("%+v", value)
+	}
+}
diff --git a/vendor/github.com/jbenet/go-context/LICENSE b/vendor/github.com/jbenet/go-context/LICENSE
new file mode 100644
index 00000000..c7386b3c
--- /dev/null
+++ b/vendor/github.com/jbenet/go-context/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 Juan Batiz-Benet
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/vendor/github.com/jbenet/go-context/io/ctxio.go b/vendor/github.com/jbenet/go-context/io/ctxio.go
new file mode 100644
index 00000000..b4f24542
--- /dev/null
+++ b/vendor/github.com/jbenet/go-context/io/ctxio.go
@@ -0,0 +1,120 @@
+// Package ctxio provides io.Reader and io.Writer wrappers that
+// respect context.Contexts. Use these at the interface between
+// your context code and your io.
+//
+// WARNING: read the code. see how writes and reads will continue
+// until you cancel the io. Maybe this package should provide
+// versions of io.ReadCloser and io.WriteCloser that automatically
+// call .Close when the context expires. But for now -- since in my
+// use cases I have long-lived connections with ephemeral io wrappers
+// -- this has yet to be a need.
+package ctxio
+
+import (
+	"io"
+
+	context "golang.org/x/net/context"
+)
+
+type ioret struct {
+	n   int
+	err error
+}
+
+type Writer interface {
+	io.Writer
+}
+
+type ctxWriter struct {
+	w   io.Writer
+	ctx context.Context
+}
+
+// NewWriter wraps a writer to make it respect given Context.
+// If there is a blocking write, the returned Writer will return
+// whenever the context is cancelled (the return values are n=0
+// and err=ctx.Err().)
+//
+// Note well: this wrapper DOES NOT ACTUALLY cancel the underlying
+// write-- there is no way to do that with the standard go io
+// interface. So the read and write _will_ happen or hang. So, use
+// this sparingly, make sure to cancel the read or write as necesary
+// (e.g. closing a connection whose context is up, etc.)
+//
+// Furthermore, in order to protect your memory from being read
+// _after_ you've cancelled the context, this io.Writer will
+// first make a **copy** of the buffer.
+func NewWriter(ctx context.Context, w io.Writer) *ctxWriter {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	return &ctxWriter{ctx: ctx, w: w}
+}
+
+func (w *ctxWriter) Write(buf []byte) (int, error) {
+	buf2 := make([]byte, len(buf))
+	copy(buf2, buf)
+
+	c := make(chan ioret, 1)
+
+	go func() {
+		n, err := w.w.Write(buf2)
+		c <- ioret{n, err}
+		close(c)
+	}()
+
+	select {
+	case r := <-c:
+		return r.n, r.err
+	case <-w.ctx.Done():
+		return 0, w.ctx.Err()
+	}
+}
+
+type Reader interface {
+	io.Reader
+}
+
+type ctxReader struct {
+	r   io.Reader
+	ctx context.Context
+}
+
+// NewReader wraps a reader to make it respect given Context.
+// If there is a blocking read, the returned Reader will return
+// whenever the context is cancelled (the return values are n=0
+// and err=ctx.Err().)
+//
+// Note well: this wrapper DOES NOT ACTUALLY cancel the underlying
+// write-- there is no way to do that with the standard go io
+// interface. So the read and write _will_ happen or hang. So, use
+// this sparingly, make sure to cancel the read or write as necesary
+// (e.g. closing a connection whose context is up, etc.)
+//
+// Furthermore, in order to protect your memory from being read
+// _before_ you've cancelled the context, this io.Reader will
+// allocate a buffer of the same size, and **copy** into the client's
+// if the read succeeds in time.
+func NewReader(ctx context.Context, r io.Reader) *ctxReader {
+	return &ctxReader{ctx: ctx, r: r}
+}
+
+func (r *ctxReader) Read(buf []byte) (int, error) {
+	buf2 := make([]byte, len(buf))
+
+	c := make(chan ioret, 1)
+
+	go func() {
+		n, err := r.r.Read(buf2)
+		c <- ioret{n, err}
+		close(c)
+	}()
+
+	select {
+	case ret := <-c:
+		copy(buf, buf2)
+		return ret.n, ret.err
+	case <-r.ctx.Done():
+		return 0, r.ctx.Err()
+	}
+}
diff --git a/vendor/github.com/kevinburke/ssh_config/.gitattributes b/vendor/github.com/kevinburke/ssh_config/.gitattributes
new file mode 100644
index 00000000..44db5818
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/.gitattributes
@@ -0,0 +1 @@
+testdata/dos-lines eol=crlf
diff --git a/vendor/github.com/kevinburke/ssh_config/.gitignore b/vendor/github.com/kevinburke/ssh_config/.gitignore
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/.gitignore
diff --git a/vendor/github.com/kevinburke/ssh_config/.mailmap b/vendor/github.com/kevinburke/ssh_config/.mailmap
new file mode 100644
index 00000000..253406b1
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/.mailmap
@@ -0,0 +1 @@
+Kevin Burke <kevin@burke.dev> Kevin Burke <kev@inburke.com>
diff --git a/vendor/github.com/kevinburke/ssh_config/.travis.yml b/vendor/github.com/kevinburke/ssh_config/.travis.yml
new file mode 100644
index 00000000..4306f30f
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/.travis.yml
@@ -0,0 +1,14 @@
+go_import_path: github.com/kevinburke/ssh_config
+
+language: go
+
+go:
+  - 1.11.x
+  - 1.12.x
+  - master
+
+before_script:
+    - go get -u ./...
+
+script:
+    - make race-test
diff --git a/vendor/github.com/kevinburke/ssh_config/AUTHORS.txt b/vendor/github.com/kevinburke/ssh_config/AUTHORS.txt
new file mode 100644
index 00000000..cd337940
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/AUTHORS.txt
@@ -0,0 +1,5 @@
+Eugene Terentev <eugene@terentev.net>
+Kevin Burke <kevin@burke.dev>
+Mark Nevill <nev@improbable.io>
+Sergey Lukjanov <me@slukjanov.name>
+Wayne Ashley Berry <wayneashleyberry@gmail.com>
diff --git a/vendor/github.com/kevinburke/ssh_config/LICENSE b/vendor/github.com/kevinburke/ssh_config/LICENSE
new file mode 100644
index 00000000..b9a770ac
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/LICENSE
@@ -0,0 +1,49 @@
+Copyright (c) 2017 Kevin Burke.
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+===================
+
+The lexer and parser borrow heavily from github.com/pelletier/go-toml. The
+license for that project is copied below.
+
+The MIT License (MIT)
+
+Copyright (c) 2013 - 2017 Thomas Pelletier, Eric Anderton
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/vendor/github.com/kevinburke/ssh_config/Makefile b/vendor/github.com/kevinburke/ssh_config/Makefile
new file mode 100644
index 00000000..a1880d18
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/Makefile
@@ -0,0 +1,30 @@
+BUMP_VERSION := $(GOPATH)/bin/bump_version
+STATICCHECK := $(GOPATH)/bin/staticcheck
+WRITE_MAILMAP := $(GOPATH)/bin/write_mailmap
+
+$(STATICCHECK):
+	go get honnef.co/go/tools/cmd/staticcheck
+
+lint: $(STATICCHECK)
+	go vet ./...
+	$(STATICCHECK)
+
+test: lint
+	@# the timeout helps guard against infinite recursion
+	go test -timeout=250ms ./...
+
+race-test: lint
+	go test -timeout=500ms -race ./...
+
+$(BUMP_VERSION):
+	go get -u github.com/kevinburke/bump_version
+
+release: test | $(BUMP_VERSION)
+	$(BUMP_VERSION) minor config.go
+
+force: ;
+
+AUTHORS.txt: force | $(WRITE_MAILMAP)
+	$(WRITE_MAILMAP) > AUTHORS.txt
+
+authors: AUTHORS.txt
diff --git a/vendor/github.com/kevinburke/ssh_config/README.md b/vendor/github.com/kevinburke/ssh_config/README.md
new file mode 100644
index 00000000..52cc1eac
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/README.md
@@ -0,0 +1,81 @@
+# ssh_config
+
+This is a Go parser for `ssh_config` files. Importantly, this parser attempts
+to preserve comments in a given file, so you can manipulate a `ssh_config` file
+from a program, if your heart desires.
+
+It's designed to be used with the excellent
+[x/crypto/ssh](https://golang.org/x/crypto/ssh) package, which handles SSH
+negotiation but isn't very easy to configure.
+
+The `ssh_config` `Get()` and `GetStrict()` functions will attempt to read values
+from `$HOME/.ssh/config` and fall back to `/etc/ssh/ssh_config`. The first
+argument is the host name to match on, and the second argument is the key you
+want to retrieve.
+
+```go
+port := ssh_config.Get("myhost", "Port")
+```
+
+You can also load a config file and read values from it.
+
+```go
+var config = `
+Host *.test
+  Compression yes
+`
+
+cfg, err := ssh_config.Decode(strings.NewReader(config))
+fmt.Println(cfg.Get("example.test", "Port"))
+```
+
+Some SSH arguments have default values - for example, the default value for
+`KeyboardAuthentication` is `"yes"`. If you call Get(), and no value for the
+given Host/keyword pair exists in the config, we'll return a default for the
+keyword if one exists.
+
+### Manipulating SSH config files
+
+Here's how you can manipulate an SSH config file, and then write it back to
+disk.
+
+```go
+f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
+cfg, _ := ssh_config.Decode(f)
+for _, host := range cfg.Hosts {
+    fmt.Println("patterns:", host.Patterns)
+    for _, node := range host.Nodes {
+        // Manipulate the nodes as you see fit, or use a type switch to
+        // distinguish between Empty, KV, and Include nodes.
+        fmt.Println(node.String())
+    }
+}
+
+// Print the config to stdout:
+fmt.Println(cfg.String())
+```
+
+## Spec compliance
+
+Wherever possible we try to implement the specification as documented in
+the `ssh_config` manpage. Unimplemented features should be present in the
+[issues][issues] list.
+
+Notably, the `Match` directive is currently unsupported.
+
+[issues]: https://github.com/kevinburke/ssh_config/issues
+
+## Errata
+
+This is the second [comment-preserving configuration parser][blog] I've written, after
+[an /etc/hosts parser][hostsfile]. Eventually, I will write one for every Linux
+file format.
+
+[blog]: https://kev.inburke.com/kevin/more-comment-preserving-configuration-parsers/
+[hostsfile]: https://github.com/kevinburke/hostsfile
+
+## Donating
+
+Donations free up time to make improvements to the library, and respond to
+bug reports. You can send donations via Paypal's "Send Money" feature to
+kev@inburke.com. Donations are not tax deductible in the USA.
diff --git a/vendor/github.com/kevinburke/ssh_config/config.go b/vendor/github.com/kevinburke/ssh_config/config.go
new file mode 100644
index 00000000..136f0c35
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/config.go
@@ -0,0 +1,649 @@
+// Package ssh_config provides tools for manipulating SSH config files.
+//
+// Importantly, this parser attempts to preserve comments in a given file, so
+// you can manipulate a `ssh_config` file from a program, if your heart desires.
+//
+// The Get() and GetStrict() functions will attempt to read values from
+// $HOME/.ssh/config, falling back to /etc/ssh/ssh_config. The first argument is
+// the host name to match on ("example.com"), and the second argument is the key
+// you want to retrieve ("Port"). The keywords are case insensitive.
+//
+// 		port := ssh_config.Get("myhost", "Port")
+//
+// You can also manipulate an SSH config file and then print it or write it back
+// to disk.
+//
+//	f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
+//	cfg, _ := ssh_config.Decode(f)
+//	for _, host := range cfg.Hosts {
+//		fmt.Println("patterns:", host.Patterns)
+//		for _, node := range host.Nodes {
+//			fmt.Println(node.String())
+//		}
+//	}
+//
+//	// Write the cfg back to disk:
+//	fmt.Println(cfg.String())
+//
+// BUG: the Match directive is currently unsupported; parsing a config with
+// a Match directive will trigger an error.
+package ssh_config
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	osuser "os/user"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+const version = "1.0"
+
+var _ = version
+
+type configFinder func() string
+
+// UserSettings checks ~/.ssh and /etc/ssh for configuration files. The config
+// files are parsed and cached the first time Get() or GetStrict() is called.
+type UserSettings struct {
+	IgnoreErrors       bool
+	systemConfig       *Config
+	systemConfigFinder configFinder
+	userConfig         *Config
+	userConfigFinder   configFinder
+	loadConfigs        sync.Once
+	onceErr            error
+}
+
+func homedir() string {
+	user, err := osuser.Current()
+	if err == nil {
+		return user.HomeDir
+	} else {
+		return os.Getenv("HOME")
+	}
+}
+
+func userConfigFinder() string {
+	return filepath.Join(homedir(), ".ssh", "config")
+}
+
+// DefaultUserSettings is the default UserSettings and is used by Get and
+// GetStrict. It checks both $HOME/.ssh/config and /etc/ssh/ssh_config for keys,
+// and it will return parse errors (if any) instead of swallowing them.
+var DefaultUserSettings = &UserSettings{
+	IgnoreErrors:       false,
+	systemConfigFinder: systemConfigFinder,
+	userConfigFinder:   userConfigFinder,
+}
+
+func systemConfigFinder() string {
+	return filepath.Join("/", "etc", "ssh", "ssh_config")
+}
+
+func findVal(c *Config, alias, key string) (string, error) {
+	if c == nil {
+		return "", nil
+	}
+	val, err := c.Get(alias, key)
+	if err != nil || val == "" {
+		return "", err
+	}
+	if err := validate(key, val); err != nil {
+		return "", err
+	}
+	return val, nil
+}
+
+// Get finds the first value for key within a declaration that matches the
+// alias. Get returns the empty string if no value was found, or if IgnoreErrors
+// is false and we could not parse the configuration file. Use GetStrict to
+// disambiguate the latter cases.
+//
+// The match for key is case insensitive.
+//
+// Get is a wrapper around DefaultUserSettings.Get.
+func Get(alias, key string) string {
+	return DefaultUserSettings.Get(alias, key)
+}
+
+// GetStrict finds the first value for key within a declaration that matches the
+// alias. If key has a default value and no matching configuration is found, the
+// default will be returned. For more information on default values and the way
+// patterns are matched, see the manpage for ssh_config.
+//
+// error will be non-nil if and only if a user's configuration file or the
+// system configuration file could not be parsed, and u.IgnoreErrors is false.
+//
+// GetStrict is a wrapper around DefaultUserSettings.GetStrict.
+func GetStrict(alias, key string) (string, error) {
+	return DefaultUserSettings.GetStrict(alias, key)
+}
+
+// Get finds the first value for key within a declaration that matches the
+// alias. Get returns the empty string if no value was found, or if IgnoreErrors
+// is false and we could not parse the configuration file. Use GetStrict to
+// disambiguate the latter cases.
+//
+// The match for key is case insensitive.
+func (u *UserSettings) Get(alias, key string) string {
+	val, err := u.GetStrict(alias, key)
+	if err != nil {
+		return ""
+	}
+	return val
+}
+
+// GetStrict finds the first value for key within a declaration that matches the
+// alias. If key has a default value and no matching configuration is found, the
+// default will be returned. For more information on default values and the way
+// patterns are matched, see the manpage for ssh_config.
+//
+// error will be non-nil if and only if a user's configuration file or the
+// system configuration file could not be parsed, and u.IgnoreErrors is false.
+func (u *UserSettings) GetStrict(alias, key string) (string, error) {
+	u.loadConfigs.Do(func() {
+		// can't parse user file, that's ok.
+		var filename string
+		if u.userConfigFinder == nil {
+			filename = userConfigFinder()
+		} else {
+			filename = u.userConfigFinder()
+		}
+		var err error
+		u.userConfig, err = parseFile(filename)
+		//lint:ignore S1002 I prefer it this way
+		if err != nil && os.IsNotExist(err) == false {
+			u.onceErr = err
+			return
+		}
+		if u.systemConfigFinder == nil {
+			filename = systemConfigFinder()
+		} else {
+			filename = u.systemConfigFinder()
+		}
+		u.systemConfig, err = parseFile(filename)
+		//lint:ignore S1002 I prefer it this way
+		if err != nil && os.IsNotExist(err) == false {
+			u.onceErr = err
+			return
+		}
+	})
+	//lint:ignore S1002 I prefer it this way
+	if u.onceErr != nil && u.IgnoreErrors == false {
+		return "", u.onceErr
+	}
+	val, err := findVal(u.userConfig, alias, key)
+	if err != nil || val != "" {
+		return val, err
+	}
+	val2, err2 := findVal(u.systemConfig, alias, key)
+	if err2 != nil || val2 != "" {
+		return val2, err2
+	}
+	return Default(key), nil
+}
+
+func parseFile(filename string) (*Config, error) {
+	return parseWithDepth(filename, 0)
+}
+
+func parseWithDepth(filename string, depth uint8) (*Config, error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return decodeBytes(b, isSystem(filename), depth)
+}
+
+func isSystem(filename string) bool {
+	// TODO: not sure this is the best way to detect a system repo
+	return strings.HasPrefix(filepath.Clean(filename), "/etc/ssh")
+}
+
+// Decode reads r into a Config, or returns an error if r could not be parsed as
+// an SSH config file.
+func Decode(r io.Reader) (*Config, error) {
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	return decodeBytes(b, false, 0)
+}
+
+func decodeBytes(b []byte, system bool, depth uint8) (c *Config, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if _, ok := r.(runtime.Error); ok {
+				panic(r)
+			}
+			if e, ok := r.(error); ok && e == ErrDepthExceeded {
+				err = e
+				return
+			}
+			err = errors.New(r.(string))
+		}
+	}()
+
+	c = parseSSH(lexSSH(b), system, depth)
+	return c, err
+}
+
+// Config represents an SSH config file.
+type Config struct {
+	// A list of hosts to match against. The file begins with an implicit
+	// "Host *" declaration matching all hosts.
+	Hosts    []*Host
+	depth    uint8
+	position Position
+}
+
+// Get finds the first value in the configuration that matches the alias and
+// contains key. Get returns the empty string if no value was found, or if the
+// Config contains an invalid conditional Include value.
+//
+// The match for key is case insensitive.
+func (c *Config) Get(alias, key string) (string, error) {
+	lowerKey := strings.ToLower(key)
+	for _, host := range c.Hosts {
+		if !host.Matches(alias) {
+			continue
+		}
+		for _, node := range host.Nodes {
+			switch t := node.(type) {
+			case *Empty:
+				continue
+			case *KV:
+				// "keys are case insensitive" per the spec
+				lkey := strings.ToLower(t.Key)
+				if lkey == "match" {
+					panic("can't handle Match directives")
+				}
+				if lkey == lowerKey {
+					return t.Value, nil
+				}
+			case *Include:
+				val := t.Get(alias, key)
+				if val != "" {
+					return val, nil
+				}
+			default:
+				return "", fmt.Errorf("unknown Node type %v", t)
+			}
+		}
+	}
+	return "", nil
+}
+
+// String returns a string representation of the Config file.
+func (c Config) String() string {
+	return marshal(c).String()
+}
+
+func (c Config) MarshalText() ([]byte, error) {
+	return marshal(c).Bytes(), nil
+}
+
+func marshal(c Config) *bytes.Buffer {
+	var buf bytes.Buffer
+	for i := range c.Hosts {
+		buf.WriteString(c.Hosts[i].String())
+	}
+	return &buf
+}
+
+// Pattern is a pattern in a Host declaration. Patterns are read-only values;
+// create a new one with NewPattern().
+type Pattern struct {
+	str   string // Its appearance in the file, not the value that gets compiled.
+	regex *regexp.Regexp
+	not   bool // True if this is a negated match
+}
+
+// String prints the string representation of the pattern.
+func (p Pattern) String() string {
+	return p.str
+}
+
+// Copied from regexp.go with * and ? removed.
+var specialBytes = []byte(`\.+()|[]{}^$`)
+
+func special(b byte) bool {
+	return bytes.IndexByte(specialBytes, b) >= 0
+}
+
+// NewPattern creates a new Pattern for matching hosts. NewPattern("*") creates
+// a Pattern that matches all hosts.
+//
+// From the manpage, a pattern consists of zero or more non-whitespace
+// characters, `*' (a wildcard that matches zero or more characters), or `?' (a
+// wildcard that matches exactly one character). For example, to specify a set
+// of declarations for any host in the ".co.uk" set of domains, the following
+// pattern could be used:
+//
+//	Host *.co.uk
+//
+// The following pattern would match any host in the 192.168.0.[0-9] network range:
+//
+//	Host 192.168.0.?
+func NewPattern(s string) (*Pattern, error) {
+	if s == "" {
+		return nil, errors.New("ssh_config: empty pattern")
+	}
+	negated := false
+	if s[0] == '!' {
+		negated = true
+		s = s[1:]
+	}
+	var buf bytes.Buffer
+	buf.WriteByte('^')
+	for i := 0; i < len(s); i++ {
+		// A byte loop is correct because all metacharacters are ASCII.
+		switch b := s[i]; b {
+		case '*':
+			buf.WriteString(".*")
+		case '?':
+			buf.WriteString(".?")
+		default:
+			// borrowing from QuoteMeta here.
+			if special(b) {
+				buf.WriteByte('\\')
+			}
+			buf.WriteByte(b)
+		}
+	}
+	buf.WriteByte('$')
+	r, err := regexp.Compile(buf.String())
+	if err != nil {
+		return nil, err
+	}
+	return &Pattern{str: s, regex: r, not: negated}, nil
+}
+
+// Host describes a Host directive and the keywords that follow it.
+type Host struct {
+	// A list of host patterns that should match this host.
+	Patterns []*Pattern
+	// A Node is either a key/value pair or a comment line.
+	Nodes []Node
+	// EOLComment is the comment (if any) terminating the Host line.
+	EOLComment   string
+	hasEquals    bool
+	leadingSpace int // TODO: handle spaces vs tabs here.
+	// The file starts with an implicit "Host *" declaration.
+	implicit bool
+}
+
+// Matches returns true if the Host matches for the given alias. For
+// a description of the rules that provide a match, see the manpage for
+// ssh_config.
+func (h *Host) Matches(alias string) bool {
+	found := false
+	for i := range h.Patterns {
+		if h.Patterns[i].regex.MatchString(alias) {
+			if h.Patterns[i].not {
+				// Negated match. "A pattern entry may be negated by prefixing
+				// it with an exclamation mark (`!'). If a negated entry is
+				// matched, then the Host entry is ignored, regardless of
+				// whether any other patterns on the line match. Negated matches
+				// are therefore useful to provide exceptions for wildcard
+				// matches."
+				return false
+			}
+			found = true
+		}
+	}
+	return found
+}
+
+// String prints h as it would appear in a config file. Minor tweaks may be
+// present in the whitespace in the printed file.
+func (h *Host) String() string {
+	var buf bytes.Buffer
+	//lint:ignore S1002 I prefer to write it this way
+	if h.implicit == false {
+		buf.WriteString(strings.Repeat(" ", int(h.leadingSpace)))
+		buf.WriteString("Host")
+		if h.hasEquals {
+			buf.WriteString(" = ")
+		} else {
+			buf.WriteString(" ")
+		}
+		for i, pat := range h.Patterns {
+			buf.WriteString(pat.String())
+			if i < len(h.Patterns)-1 {
+				buf.WriteString(" ")
+			}
+		}
+		if h.EOLComment != "" {
+			buf.WriteString(" #")
+			buf.WriteString(h.EOLComment)
+		}
+		buf.WriteByte('\n')
+	}
+	for i := range h.Nodes {
+		buf.WriteString(h.Nodes[i].String())
+		buf.WriteByte('\n')
+	}
+	return buf.String()
+}
+
+// Node represents a line in a Config.
+type Node interface {
+	Pos() Position
+	String() string
+}
+
+// KV is a line in the config file that contains a key, a value, and possibly
+// a comment.
+type KV struct {
+	Key          string
+	Value        string
+	Comment      string
+	hasEquals    bool
+	leadingSpace int // Space before the key. TODO handle spaces vs tabs.
+	position     Position
+}
+
+// Pos returns k's Position.
+func (k *KV) Pos() Position {
+	return k.position
+}
+
+// String prints k as it was parsed in the config file. There may be slight
+// changes to the whitespace between values.
+func (k *KV) String() string {
+	if k == nil {
+		return ""
+	}
+	equals := " "
+	if k.hasEquals {
+		equals = " = "
+	}
+	line := fmt.Sprintf("%s%s%s%s", strings.Repeat(" ", int(k.leadingSpace)), k.Key, equals, k.Value)
+	if k.Comment != "" {
+		line += " #" + k.Comment
+	}
+	return line
+}
+
+// Empty is a line in the config file that contains only whitespace or comments.
+type Empty struct {
+	Comment      string
+	leadingSpace int // TODO handle spaces vs tabs.
+	position     Position
+}
+
+// Pos returns e's Position.
+func (e *Empty) Pos() Position {
+	return e.position
+}
+
+// String prints e as it was parsed in the config file.
+func (e *Empty) String() string {
+	if e == nil {
+		return ""
+	}
+	if e.Comment == "" {
+		return ""
+	}
+	return fmt.Sprintf("%s#%s", strings.Repeat(" ", int(e.leadingSpace)), e.Comment)
+}
+
+// Include holds the result of an Include directive, including the config files
+// that have been parsed as part of that directive. At most 5 levels of Include
+// statements will be parsed.
+type Include struct {
+	// Comment is the contents of any comment at the end of the Include
+	// statement.
+	Comment string
+	// an include directive can include several different files, and wildcards
+	directives []string
+
+	mu sync.Mutex
+	// 1:1 mapping between matches and keys in files array; matches preserves
+	// ordering
+	matches []string
+	// actual filenames are listed here
+	files        map[string]*Config
+	leadingSpace int
+	position     Position
+	depth        uint8
+	hasEquals    bool
+}
+
+const maxRecurseDepth = 5
+
+// ErrDepthExceeded is returned if too many Include directives are parsed.
+// Usually this indicates a recursive loop (an Include directive pointing to the
+// file it contains).
+var ErrDepthExceeded = errors.New("ssh_config: max recurse depth exceeded")
+
+func removeDups(arr []string) []string {
+	// Use map to record duplicates as we find them.
+	encountered := make(map[string]bool, len(arr))
+	result := make([]string, 0)
+
+	for v := range arr {
+		//lint:ignore S1002 I prefer it this way
+		if encountered[arr[v]] == false {
+			encountered[arr[v]] = true
+			result = append(result, arr[v])
+		}
+	}
+	return result
+}
+
+// NewInclude creates a new Include with a list of file globs to include.
+// Configuration files are parsed greedily (e.g. as soon as this function runs).
+// Any error encountered while parsing nested configuration files will be
+// returned.
+func NewInclude(directives []string, hasEquals bool, pos Position, comment string, system bool, depth uint8) (*Include, error) {
+	if depth > maxRecurseDepth {
+		return nil, ErrDepthExceeded
+	}
+	inc := &Include{
+		Comment:      comment,
+		directives:   directives,
+		files:        make(map[string]*Config),
+		position:     pos,
+		leadingSpace: pos.Col - 1,
+		depth:        depth,
+		hasEquals:    hasEquals,
+	}
+	// no need for inc.mu.Lock() since nothing else can access this inc
+	matches := make([]string, 0)
+	for i := range directives {
+		var path string
+		if filepath.IsAbs(directives[i]) {
+			path = directives[i]
+		} else if system {
+			path = filepath.Join("/etc/ssh", directives[i])
+		} else {
+			path = filepath.Join(homedir(), ".ssh", directives[i])
+		}
+		theseMatches, err := filepath.Glob(path)
+		if err != nil {
+			return nil, err
+		}
+		matches = append(matches, theseMatches...)
+	}
+	matches = removeDups(matches)
+	inc.matches = matches
+	for i := range matches {
+		config, err := parseWithDepth(matches[i], depth)
+		if err != nil {
+			return nil, err
+		}
+		inc.files[matches[i]] = config
+	}
+	return inc, nil
+}
+
+// Pos returns the position of the Include directive in the larger file.
+func (i *Include) Pos() Position {
+	return i.position
+}
+
+// Get finds the first value in the Include statement matching the alias and the
+// given key.
+func (inc *Include) Get(alias, key string) string {
+	inc.mu.Lock()
+	defer inc.mu.Unlock()
+	// TODO: we search files in any order which is not correct
+	for i := range inc.matches {
+		cfg := inc.files[inc.matches[i]]
+		if cfg == nil {
+			panic("nil cfg")
+		}
+		val, err := cfg.Get(alias, key)
+		if err == nil && val != "" {
+			return val
+		}
+	}
+	return ""
+}
+
+// String prints out a string representation of this Include directive. Note
+// included Config files are not printed as part of this representation.
+func (inc *Include) String() string {
+	equals := " "
+	if inc.hasEquals {
+		equals = " = "
+	}
+	line := fmt.Sprintf("%sInclude%s%s", strings.Repeat(" ", int(inc.leadingSpace)), equals, strings.Join(inc.directives, " "))
+	if inc.Comment != "" {
+		line += " #" + inc.Comment
+	}
+	return line
+}
+
+var matchAll *Pattern
+
+func init() {
+	var err error
+	matchAll, err = NewPattern("*")
+	if err != nil {
+		panic(err)
+	}
+}
+
+func newConfig() *Config {
+	return &Config{
+		Hosts: []*Host{
+			&Host{
+				implicit: true,
+				Patterns: []*Pattern{matchAll},
+				Nodes:    make([]Node, 0),
+			},
+		},
+		depth: 0,
+	}
+}
diff --git a/vendor/github.com/kevinburke/ssh_config/lexer.go b/vendor/github.com/kevinburke/ssh_config/lexer.go
new file mode 100644
index 00000000..11680b4c
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/lexer.go
@@ -0,0 +1,240 @@
+package ssh_config
+
+import (
+	"bytes"
+)
+
+// Define state functions
+type sshLexStateFn func() sshLexStateFn
+
+type sshLexer struct {
+	inputIdx int
+	input    []rune // Textual source
+
+	buffer        []rune // Runes composing the current token
+	tokens        chan token
+	line          int
+	col           int
+	endbufferLine int
+	endbufferCol  int
+}
+
+func (s *sshLexer) lexComment(previousState sshLexStateFn) sshLexStateFn {
+	return func() sshLexStateFn {
+		growingString := ""
+		for next := s.peek(); next != '\n' && next != eof; next = s.peek() {
+			if next == '\r' && s.follow("\r\n") {
+				break
+			}
+			growingString += string(next)
+			s.next()
+		}
+		s.emitWithValue(tokenComment, growingString)
+		s.skip()
+		return previousState
+	}
+}
+
+// lex the space after an equals sign in a function
+func (s *sshLexer) lexRspace() sshLexStateFn {
+	for {
+		next := s.peek()
+		if !isSpace(next) {
+			break
+		}
+		s.skip()
+	}
+	return s.lexRvalue
+}
+
+func (s *sshLexer) lexEquals() sshLexStateFn {
+	for {
+		next := s.peek()
+		if next == '=' {
+			s.emit(tokenEquals)
+			s.skip()
+			return s.lexRspace
+		}
+		// TODO error handling here; newline eof etc.
+		if !isSpace(next) {
+			break
+		}
+		s.skip()
+	}
+	return s.lexRvalue
+}
+
+func (s *sshLexer) lexKey() sshLexStateFn {
+	growingString := ""
+
+	for r := s.peek(); isKeyChar(r); r = s.peek() {
+		// simplified a lot here
+		if isSpace(r) || r == '=' {
+			s.emitWithValue(tokenKey, growingString)
+			s.skip()
+			return s.lexEquals
+		}
+		growingString += string(r)
+		s.next()
+	}
+	s.emitWithValue(tokenKey, growingString)
+	return s.lexEquals
+}
+
+func (s *sshLexer) lexRvalue() sshLexStateFn {
+	growingString := ""
+	for {
+		next := s.peek()
+		switch next {
+		case '\r':
+			if s.follow("\r\n") {
+				s.emitWithValue(tokenString, growingString)
+				s.skip()
+				return s.lexVoid
+			}
+		case '\n':
+			s.emitWithValue(tokenString, growingString)
+			s.skip()
+			return s.lexVoid
+		case '#':
+			s.emitWithValue(tokenString, growingString)
+			s.skip()
+			return s.lexComment(s.lexVoid)
+		case eof:
+			s.next()
+		}
+		if next == eof {
+			break
+		}
+		growingString += string(next)
+		s.next()
+	}
+	s.emit(tokenEOF)
+	return nil
+}
+
+func (s *sshLexer) read() rune {
+	r := s.peek()
+	if r == '\n' {
+		s.endbufferLine++
+		s.endbufferCol = 1
+	} else {
+		s.endbufferCol++
+	}
+	s.inputIdx++
+	return r
+}
+
+func (s *sshLexer) next() rune {
+	r := s.read()
+
+	if r != eof {
+		s.buffer = append(s.buffer, r)
+	}
+	return r
+}
+
+func (s *sshLexer) lexVoid() sshLexStateFn {
+	for {
+		next := s.peek()
+		switch next {
+		case '#':
+			s.skip()
+			return s.lexComment(s.lexVoid)
+		case '\r':
+			fallthrough
+		case '\n':
+			s.emit(tokenEmptyLine)
+			s.skip()
+			continue
+		}
+
+		if isSpace(next) {
+			s.skip()
+		}
+
+		if isKeyStartChar(next) {
+			return s.lexKey
+		}
+
+		// removed IsKeyStartChar and lexKey. probably will need to readd
+
+		if next == eof {
+			s.next()
+			break
+		}
+	}
+
+	s.emit(tokenEOF)
+	return nil
+}
+
+func (s *sshLexer) ignore() {
+	s.buffer = make([]rune, 0)
+	s.line = s.endbufferLine
+	s.col = s.endbufferCol
+}
+
+func (s *sshLexer) skip() {
+	s.next()
+	s.ignore()
+}
+
+func (s *sshLexer) emit(t tokenType) {
+	s.emitWithValue(t, string(s.buffer))
+}
+
+func (s *sshLexer) emitWithValue(t tokenType, value string) {
+	tok := token{
+		Position: Position{s.line, s.col},
+		typ:      t,
+		val:      value,
+	}
+	s.tokens <- tok
+	s.ignore()
+}
+
+func (s *sshLexer) peek() rune {
+	if s.inputIdx >= len(s.input) {
+		return eof
+	}
+
+	r := s.input[s.inputIdx]
+	return r
+}
+
+func (s *sshLexer) follow(next string) bool {
+	inputIdx := s.inputIdx
+	for _, expectedRune := range next {
+		if inputIdx >= len(s.input) {
+			return false
+		}
+		r := s.input[inputIdx]
+		inputIdx++
+		if expectedRune != r {
+			return false
+		}
+	}
+	return true
+}
+
+func (s *sshLexer) run() {
+	for state := s.lexVoid; state != nil; {
+		state = state()
+	}
+	close(s.tokens)
+}
+
+func lexSSH(input []byte) chan token {
+	runes := bytes.Runes(input)
+	l := &sshLexer{
+		input:         runes,
+		tokens:        make(chan token),
+		line:          1,
+		col:           1,
+		endbufferLine: 1,
+		endbufferCol:  1,
+	}
+	go l.run()
+	return l.tokens
+}
diff --git a/vendor/github.com/kevinburke/ssh_config/parser.go b/vendor/github.com/kevinburke/ssh_config/parser.go
new file mode 100644
index 00000000..36c42055
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/parser.go
@@ -0,0 +1,191 @@
+package ssh_config
+
+import (
+	"fmt"
+	"strings"
+)
+
+type sshParser struct {
+	flow          chan token
+	config        *Config
+	tokensBuffer  []token
+	currentTable  []string
+	seenTableKeys []string
+	// /etc/ssh parser or local parser - used to find the default for relative
+	// filepaths in the Include directive
+	system bool
+	depth  uint8
+}
+
+type sshParserStateFn func() sshParserStateFn
+
+// Formats and panics an error message based on a token
+func (p *sshParser) raiseErrorf(tok *token, msg string, args ...interface{}) {
+	// TODO this format is ugly
+	panic(tok.Position.String() + ": " + fmt.Sprintf(msg, args...))
+}
+
+func (p *sshParser) raiseError(tok *token, err error) {
+	if err == ErrDepthExceeded {
+		panic(err)
+	}
+	// TODO this format is ugly
+	panic(tok.Position.String() + ": " + err.Error())
+}
+
+func (p *sshParser) run() {
+	for state := p.parseStart; state != nil; {
+		state = state()
+	}
+}
+
+func (p *sshParser) peek() *token {
+	if len(p.tokensBuffer) != 0 {
+		return &(p.tokensBuffer[0])
+	}
+
+	tok, ok := <-p.flow
+	if !ok {
+		return nil
+	}
+	p.tokensBuffer = append(p.tokensBuffer, tok)
+	return &tok
+}
+
+func (p *sshParser) getToken() *token {
+	if len(p.tokensBuffer) != 0 {
+		tok := p.tokensBuffer[0]
+		p.tokensBuffer = p.tokensBuffer[1:]
+		return &tok
+	}
+	tok, ok := <-p.flow
+	if !ok {
+		return nil
+	}
+	return &tok
+}
+
+func (p *sshParser) parseStart() sshParserStateFn {
+	tok := p.peek()
+
+	// end of stream, parsing is finished
+	if tok == nil {
+		return nil
+	}
+
+	switch tok.typ {
+	case tokenComment, tokenEmptyLine:
+		return p.parseComment
+	case tokenKey:
+		return p.parseKV
+	case tokenEOF:
+		return nil
+	default:
+		p.raiseErrorf(tok, fmt.Sprintf("unexpected token %q\n", tok))
+	}
+	return nil
+}
+
+func (p *sshParser) parseKV() sshParserStateFn {
+	key := p.getToken()
+	hasEquals := false
+	val := p.getToken()
+	if val.typ == tokenEquals {
+		hasEquals = true
+		val = p.getToken()
+	}
+	comment := ""
+	tok := p.peek()
+	if tok == nil {
+		tok = &token{typ: tokenEOF}
+	}
+	if tok.typ == tokenComment && tok.Position.Line == val.Position.Line {
+		tok = p.getToken()
+		comment = tok.val
+	}
+	if strings.ToLower(key.val) == "match" {
+		// https://github.com/kevinburke/ssh_config/issues/6
+		p.raiseErrorf(val, "ssh_config: Match directive parsing is unsupported")
+		return nil
+	}
+	if strings.ToLower(key.val) == "host" {
+		strPatterns := strings.Split(val.val, " ")
+		patterns := make([]*Pattern, 0)
+		for i := range strPatterns {
+			if strPatterns[i] == "" {
+				continue
+			}
+			pat, err := NewPattern(strPatterns[i])
+			if err != nil {
+				p.raiseErrorf(val, "Invalid host pattern: %v", err)
+				return nil
+			}
+			patterns = append(patterns, pat)
+		}
+		p.config.Hosts = append(p.config.Hosts, &Host{
+			Patterns:   patterns,
+			Nodes:      make([]Node, 0),
+			EOLComment: comment,
+			hasEquals:  hasEquals,
+		})
+		return p.parseStart
+	}
+	lastHost := p.config.Hosts[len(p.config.Hosts)-1]
+	if strings.ToLower(key.val) == "include" {
+		inc, err := NewInclude(strings.Split(val.val, " "), hasEquals, key.Position, comment, p.system, p.depth+1)
+		if err == ErrDepthExceeded {
+			p.raiseError(val, err)
+			return nil
+		}
+		if err != nil {
+			p.raiseErrorf(val, "Error parsing Include directive: %v", err)
+			return nil
+		}
+		lastHost.Nodes = append(lastHost.Nodes, inc)
+		return p.parseStart
+	}
+	kv := &KV{
+		Key:          key.val,
+		Value:        val.val,
+		Comment:      comment,
+		hasEquals:    hasEquals,
+		leadingSpace: key.Position.Col - 1,
+		position:     key.Position,
+	}
+	lastHost.Nodes = append(lastHost.Nodes, kv)
+	return p.parseStart
+}
+
+func (p *sshParser) parseComment() sshParserStateFn {
+	comment := p.getToken()
+	lastHost := p.config.Hosts[len(p.config.Hosts)-1]
+	lastHost.Nodes = append(lastHost.Nodes, &Empty{
+		Comment: comment.val,
+		// account for the "#" as well
+		leadingSpace: comment.Position.Col - 2,
+		position:     comment.Position,
+	})
+	return p.parseStart
+}
+
+func parseSSH(flow chan token, system bool, depth uint8) *Config {
+	// Ensure we consume tokens to completion even if parser exits early
+	defer func() {
+		for range flow {
+		}
+	}()
+
+	result := newConfig()
+	result.position = Position{1, 1}
+	parser := &sshParser{
+		flow:          flow,
+		config:        result,
+		tokensBuffer:  make([]token, 0),
+		currentTable:  make([]string, 0),
+		seenTableKeys: make([]string, 0),
+		system:        system,
+		depth:         depth,
+	}
+	parser.run()
+	return result
+}
diff --git a/vendor/github.com/kevinburke/ssh_config/position.go b/vendor/github.com/kevinburke/ssh_config/position.go
new file mode 100644
index 00000000..e0b5e3fb
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/position.go
@@ -0,0 +1,25 @@
+package ssh_config
+
+import "fmt"
+
+// Position of a document element within a SSH document.
+//
+// Line and Col are both 1-indexed positions for the element's line number and
+// column number, respectively.  Values of zero or less will cause Invalid(),
+// to return true.
+type Position struct {
+	Line int // line within the document
+	Col  int // column within the line
+}
+
+// String representation of the position.
+// Displays 1-indexed line and column numbers.
+func (p Position) String() string {
+	return fmt.Sprintf("(%d, %d)", p.Line, p.Col)
+}
+
+// Invalid returns whether or not the position is valid (i.e. with negative or
+// null values)
+func (p Position) Invalid() bool {
+	return p.Line <= 0 || p.Col <= 0
+}
diff --git a/vendor/github.com/kevinburke/ssh_config/token.go b/vendor/github.com/kevinburke/ssh_config/token.go
new file mode 100644
index 00000000..a0ecbb2b
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/token.go
@@ -0,0 +1,49 @@
+package ssh_config
+
+import "fmt"
+
+type token struct {
+	Position
+	typ tokenType
+	val string
+}
+
+func (t token) String() string {
+	switch t.typ {
+	case tokenEOF:
+		return "EOF"
+	}
+	return fmt.Sprintf("%q", t.val)
+}
+
+type tokenType int
+
+const (
+	eof = -(iota + 1)
+)
+
+const (
+	tokenError tokenType = iota
+	tokenEOF
+	tokenEmptyLine
+	tokenComment
+	tokenKey
+	tokenEquals
+	tokenString
+)
+
+func isSpace(r rune) bool {
+	return r == ' ' || r == '\t'
+}
+
+func isKeyStartChar(r rune) bool {
+	return !(isSpace(r) || r == '\r' || r == '\n' || r == eof)
+}
+
+// I'm not sure that this is correct
+func isKeyChar(r rune) bool {
+	// Keys start with the first character that isn't whitespace or [ and end
+	// with the last non-whitespace character before the equals sign. Keys
+	// cannot contain a # character."
+	return !(r == '\r' || r == '\n' || r == eof || r == '=')
+}
diff --git a/vendor/github.com/kevinburke/ssh_config/validators.go b/vendor/github.com/kevinburke/ssh_config/validators.go
new file mode 100644
index 00000000..29fab6a9
--- /dev/null
+++ b/vendor/github.com/kevinburke/ssh_config/validators.go
@@ -0,0 +1,162 @@
+package ssh_config
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// Default returns the default value for the given keyword, for example "22" if
+// the keyword is "Port". Default returns the empty string if the keyword has no
+// default, or if the keyword is unknown. Keyword matching is case-insensitive.
+//
+// Default values are provided by OpenSSH_7.4p1 on a Mac.
+func Default(keyword string) string {
+	return defaults[strings.ToLower(keyword)]
+}
+
+// Arguments where the value must be "yes" or "no" and *only* yes or no.
+var yesnos = map[string]bool{
+	strings.ToLower("BatchMode"):                        true,
+	strings.ToLower("CanonicalizeFallbackLocal"):        true,
+	strings.ToLower("ChallengeResponseAuthentication"):  true,
+	strings.ToLower("CheckHostIP"):                      true,
+	strings.ToLower("ClearAllForwardings"):              true,
+	strings.ToLower("Compression"):                      true,
+	strings.ToLower("EnableSSHKeysign"):                 true,
+	strings.ToLower("ExitOnForwardFailure"):             true,
+	strings.ToLower("ForwardAgent"):                     true,
+	strings.ToLower("ForwardX11"):                       true,
+	strings.ToLower("ForwardX11Trusted"):                true,
+	strings.ToLower("GatewayPorts"):                     true,
+	strings.ToLower("GSSAPIAuthentication"):             true,
+	strings.ToLower("GSSAPIDelegateCredentials"):        true,
+	strings.ToLower("HostbasedAuthentication"):          true,
+	strings.ToLower("IdentitiesOnly"):                   true,
+	strings.ToLower("KbdInteractiveAuthentication"):     true,
+	strings.ToLower("NoHostAuthenticationForLocalhost"): true,
+	strings.ToLower("PasswordAuthentication"):           true,
+	strings.ToLower("PermitLocalCommand"):               true,
+	strings.ToLower("PubkeyAuthentication"):             true,
+	strings.ToLower("RhostsRSAAuthentication"):          true,
+	strings.ToLower("RSAAuthentication"):                true,
+	strings.ToLower("StreamLocalBindUnlink"):            true,
+	strings.ToLower("TCPKeepAlive"):                     true,
+	strings.ToLower("UseKeychain"):                      true,
+	strings.ToLower("UsePrivilegedPort"):                true,
+	strings.ToLower("VisualHostKey"):                    true,
+}
+
+var uints = map[string]bool{
+	strings.ToLower("CanonicalizeMaxDots"):     true,
+	strings.ToLower("CompressionLevel"):        true, // 1 to 9
+	strings.ToLower("ConnectionAttempts"):      true,
+	strings.ToLower("ConnectTimeout"):          true,
+	strings.ToLower("NumberOfPasswordPrompts"): true,
+	strings.ToLower("Port"):                    true,
+	strings.ToLower("ServerAliveCountMax"):     true,
+	strings.ToLower("ServerAliveInterval"):     true,
+}
+
+func mustBeYesOrNo(lkey string) bool {
+	return yesnos[lkey]
+}
+
+func mustBeUint(lkey string) bool {
+	return uints[lkey]
+}
+
+func validate(key, val string) error {
+	lkey := strings.ToLower(key)
+	if mustBeYesOrNo(lkey) && (val != "yes" && val != "no") {
+		return fmt.Errorf("ssh_config: value for key %q must be 'yes' or 'no', got %q", key, val)
+	}
+	if mustBeUint(lkey) {
+		_, err := strconv.ParseUint(val, 10, 64)
+		if err != nil {
+			return fmt.Errorf("ssh_config: %v", err)
+		}
+	}
+	return nil
+}
+
+var defaults = map[string]string{
+	strings.ToLower("AddKeysToAgent"):                  "no",
+	strings.ToLower("AddressFamily"):                   "any",
+	strings.ToLower("BatchMode"):                       "no",
+	strings.ToLower("CanonicalizeFallbackLocal"):       "yes",
+	strings.ToLower("CanonicalizeHostname"):            "no",
+	strings.ToLower("CanonicalizeMaxDots"):             "1",
+	strings.ToLower("ChallengeResponseAuthentication"): "yes",
+	strings.ToLower("CheckHostIP"):                     "yes",
+	// TODO is this still the correct cipher
+	strings.ToLower("Cipher"):                    "3des",
+	strings.ToLower("Ciphers"):                   "chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc",
+	strings.ToLower("ClearAllForwardings"):       "no",
+	strings.ToLower("Compression"):               "no",
+	strings.ToLower("CompressionLevel"):          "6",
+	strings.ToLower("ConnectionAttempts"):        "1",
+	strings.ToLower("ControlMaster"):             "no",
+	strings.ToLower("EnableSSHKeysign"):          "no",
+	strings.ToLower("EscapeChar"):                "~",
+	strings.ToLower("ExitOnForwardFailure"):      "no",
+	strings.ToLower("FingerprintHash"):           "sha256",
+	strings.ToLower("ForwardAgent"):              "no",
+	strings.ToLower("ForwardX11"):                "no",
+	strings.ToLower("ForwardX11Timeout"):         "20m",
+	strings.ToLower("ForwardX11Trusted"):         "no",
+	strings.ToLower("GatewayPorts"):              "no",
+	strings.ToLower("GlobalKnownHostsFile"):      "/etc/ssh/ssh_known_hosts /etc/ssh/ssh_known_hosts2",
+	strings.ToLower("GSSAPIAuthentication"):      "no",
+	strings.ToLower("GSSAPIDelegateCredentials"): "no",
+	strings.ToLower("HashKnownHosts"):            "no",
+	strings.ToLower("HostbasedAuthentication"):   "no",
+
+	strings.ToLower("HostbasedKeyTypes"): "ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-rsa",
+	strings.ToLower("HostKeyAlgorithms"): "ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-rsa",
+	// HostName has a dynamic default (the value passed at the command line).
+
+	strings.ToLower("IdentitiesOnly"): "no",
+	strings.ToLower("IdentityFile"):   "~/.ssh/identity",
+
+	// IPQoS has a dynamic default based on interactive or non-interactive
+	// sessions.
+
+	strings.ToLower("KbdInteractiveAuthentication"): "yes",
+
+	strings.ToLower("KexAlgorithms"): "curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1",
+	strings.ToLower("LogLevel"):      "INFO",
+	strings.ToLower("MACs"):          "umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1",
+
+	strings.ToLower("NoHostAuthenticationForLocalhost"): "no",
+	strings.ToLower("NumberOfPasswordPrompts"):          "3",
+	strings.ToLower("PasswordAuthentication"):           "yes",
+	strings.ToLower("PermitLocalCommand"):               "no",
+	strings.ToLower("Port"):                             "22",
+
+	strings.ToLower("PreferredAuthentications"): "gssapi-with-mic,hostbased,publickey,keyboard-interactive,password",
+	strings.ToLower("Protocol"):                 "2",
+	strings.ToLower("ProxyUseFdpass"):           "no",
+	strings.ToLower("PubkeyAcceptedKeyTypes"):   "ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-rsa",
+	strings.ToLower("PubkeyAuthentication"):     "yes",
+	strings.ToLower("RekeyLimit"):               "default none",
+	strings.ToLower("RhostsRSAAuthentication"):  "no",
+	strings.ToLower("RSAAuthentication"):        "yes",
+
+	strings.ToLower("ServerAliveCountMax"):   "3",
+	strings.ToLower("ServerAliveInterval"):   "0",
+	strings.ToLower("StreamLocalBindMask"):   "0177",
+	strings.ToLower("StreamLocalBindUnlink"): "no",
+	strings.ToLower("StrictHostKeyChecking"): "ask",
+	strings.ToLower("TCPKeepAlive"):          "yes",
+	strings.ToLower("Tunnel"):                "no",
+	strings.ToLower("TunnelDevice"):          "any:any",
+	strings.ToLower("UpdateHostKeys"):        "no",
+	strings.ToLower("UseKeychain"):           "no",
+	strings.ToLower("UsePrivilegedPort"):     "no",
+
+	strings.ToLower("UserKnownHostsFile"): "~/.ssh/known_hosts ~/.ssh/known_hosts2",
+	strings.ToLower("VerifyHostKeyDNS"):   "no",
+	strings.ToLower("VisualHostKey"):      "no",
+	strings.ToLower("XAuthLocation"):      "/usr/X11R6/bin/xauth",
+}
diff --git a/vendor/github.com/sergi/go-diff/AUTHORS b/vendor/github.com/sergi/go-diff/AUTHORS
new file mode 100644
index 00000000..2d7bb2bf
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/AUTHORS
@@ -0,0 +1,25 @@
+# This is the official list of go-diff authors for copyright purposes.
+# This file is distinct from the CONTRIBUTORS files.
+# See the latter for an explanation.
+
+# Names should be added to this file as
+#	Name or Organization <email address>
+# The email address is not required for organizations.
+
+# Please keep the list sorted.
+
+Danny Yoo <dannyyoo@google.com>
+James Kolb <jkolb@google.com>
+Jonathan Amsterdam <jba@google.com>
+Markus Zimmermann <markus.zimmermann@nethead.at> <markus.zimmermann@symflower.com> <zimmski@gmail.com>
+Matt Kovars <akaskik@gmail.com>
+Örjan Persson <orjan@spotify.com>
+Osman Masood <oamasood@gmail.com>
+Robert Carlsen <rwcarlsen@gmail.com>
+Rory Flynn <roryflynn@users.noreply.github.com>
+Sergi Mansilla <sergi.mansilla@gmail.com>
+Shatrugna Sadhu <ssadhu@apcera.com>
+Shawn Smith <shawnpsmith@gmail.com>
+Stas Maksimov <maksimov@gmail.com>
+Tor Arvid Lund <torarvid@gmail.com>
+Zac Bergquist <zbergquist99@gmail.com>
diff --git a/vendor/github.com/sergi/go-diff/CONTRIBUTORS b/vendor/github.com/sergi/go-diff/CONTRIBUTORS
new file mode 100644
index 00000000..369e3d55
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/CONTRIBUTORS
@@ -0,0 +1,32 @@
+# This is the official list of people who can contribute
+# (and typically have contributed) code to the go-diff
+# repository.
+#
+# The AUTHORS file lists the copyright holders; this file
+# lists people.  For example, ACME Inc. employees would be listed here
+# but not in AUTHORS, because ACME Inc. would hold the copyright.
+#
+# When adding J Random Contributor's name to this file,
+# either J's name or J's organization's name should be
+# added to the AUTHORS file.
+#
+# Names should be added to this file like so:
+#     Name <email address>
+#
+# Please keep the list sorted.
+
+Danny Yoo <dannyyoo@google.com>
+James Kolb <jkolb@google.com>
+Jonathan Amsterdam <jba@google.com>
+Markus Zimmermann <markus.zimmermann@nethead.at> <markus.zimmermann@symflower.com> <zimmski@gmail.com>
+Matt Kovars <akaskik@gmail.com>
+Örjan Persson <orjan@spotify.com>
+Osman Masood <oamasood@gmail.com>
+Robert Carlsen <rwcarlsen@gmail.com>
+Rory Flynn <roryflynn@users.noreply.github.com>
+Sergi Mansilla <sergi.mansilla@gmail.com>
+Shatrugna Sadhu <ssadhu@apcera.com>
+Shawn Smith <shawnpsmith@gmail.com>
+Stas Maksimov <maksimov@gmail.com>
+Tor Arvid Lund <torarvid@gmail.com>
+Zac Bergquist <zbergquist99@gmail.com>
diff --git a/vendor/github.com/sergi/go-diff/LICENSE b/vendor/github.com/sergi/go-diff/LICENSE
new file mode 100644
index 00000000..937942c2
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/LICENSE
@@ -0,0 +1,20 @@
+Copyright (c) 2012-2016 The go-diff Authors. All rights reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
diff --git a/vendor/github.com/sergi/go-diff/diffmatchpatch/diff.go b/vendor/github.com/sergi/go-diff/diffmatchpatch/diff.go
new file mode 100644
index 00000000..82ad7bc8
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/diffmatchpatch/diff.go
@@ -0,0 +1,1344 @@
+// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
+// https://github.com/sergi/go-diff
+// See the included LICENSE file for license details.
+//
+// go-diff is a Go implementation of Google's Diff, Match, and Patch library
+// Original library is Copyright (c) 2006 Google Inc.
+// http://code.google.com/p/google-diff-match-patch/
+
+package diffmatchpatch
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"html"
+	"math"
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+)
+
+// Operation defines the operation of a diff item.
+type Operation int8
+
+const (
+	// DiffDelete item represents a delete diff.
+	DiffDelete Operation = -1
+	// DiffInsert item represents an insert diff.
+	DiffInsert Operation = 1
+	// DiffEqual item represents an equal diff.
+	DiffEqual Operation = 0
+)
+
+// Diff represents one diff operation
+type Diff struct {
+	Type Operation
+	Text string
+}
+
+func splice(slice []Diff, index int, amount int, elements ...Diff) []Diff {
+	return append(slice[:index], append(elements, slice[index+amount:]...)...)
+}
+
+// DiffMain finds the differences between two texts.
+// If an invalid UTF-8 sequence is encountered, it will be replaced by the Unicode replacement character.
+func (dmp *DiffMatchPatch) DiffMain(text1, text2 string, checklines bool) []Diff {
+	return dmp.DiffMainRunes([]rune(text1), []rune(text2), checklines)
+}
+
+// DiffMainRunes finds the differences between two rune sequences.
+// If an invalid UTF-8 sequence is encountered, it will be replaced by the Unicode replacement character.
+func (dmp *DiffMatchPatch) DiffMainRunes(text1, text2 []rune, checklines bool) []Diff {
+	var deadline time.Time
+	if dmp.DiffTimeout > 0 {
+		deadline = time.Now().Add(dmp.DiffTimeout)
+	}
+	return dmp.diffMainRunes(text1, text2, checklines, deadline)
+}
+
+func (dmp *DiffMatchPatch) diffMainRunes(text1, text2 []rune, checklines bool, deadline time.Time) []Diff {
+	if runesEqual(text1, text2) {
+		var diffs []Diff
+		if len(text1) > 0 {
+			diffs = append(diffs, Diff{DiffEqual, string(text1)})
+		}
+		return diffs
+	}
+	// Trim off common prefix (speedup).
+	commonlength := commonPrefixLength(text1, text2)
+	commonprefix := text1[:commonlength]
+	text1 = text1[commonlength:]
+	text2 = text2[commonlength:]
+
+	// Trim off common suffix (speedup).
+	commonlength = commonSuffixLength(text1, text2)
+	commonsuffix := text1[len(text1)-commonlength:]
+	text1 = text1[:len(text1)-commonlength]
+	text2 = text2[:len(text2)-commonlength]
+
+	// Compute the diff on the middle block.
+	diffs := dmp.diffCompute(text1, text2, checklines, deadline)
+
+	// Restore the prefix and suffix.
+	if len(commonprefix) != 0 {
+		diffs = append([]Diff{Diff{DiffEqual, string(commonprefix)}}, diffs...)
+	}
+	if len(commonsuffix) != 0 {
+		diffs = append(diffs, Diff{DiffEqual, string(commonsuffix)})
+	}
+
+	return dmp.DiffCleanupMerge(diffs)
+}
+
+// diffCompute finds the differences between two rune slices.  Assumes that the texts do not have any common prefix or suffix.
+func (dmp *DiffMatchPatch) diffCompute(text1, text2 []rune, checklines bool, deadline time.Time) []Diff {
+	diffs := []Diff{}
+	if len(text1) == 0 {
+		// Just add some text (speedup).
+		return append(diffs, Diff{DiffInsert, string(text2)})
+	} else if len(text2) == 0 {
+		// Just delete some text (speedup).
+		return append(diffs, Diff{DiffDelete, string(text1)})
+	}
+
+	var longtext, shorttext []rune
+	if len(text1) > len(text2) {
+		longtext = text1
+		shorttext = text2
+	} else {
+		longtext = text2
+		shorttext = text1
+	}
+
+	if i := runesIndex(longtext, shorttext); i != -1 {
+		op := DiffInsert
+		// Swap insertions for deletions if diff is reversed.
+		if len(text1) > len(text2) {
+			op = DiffDelete
+		}
+		// Shorter text is inside the longer text (speedup).
+		return []Diff{
+			Diff{op, string(longtext[:i])},
+			Diff{DiffEqual, string(shorttext)},
+			Diff{op, string(longtext[i+len(shorttext):])},
+		}
+	} else if len(shorttext) == 1 {
+		// Single character string.
+		// After the previous speedup, the character can't be an equality.
+		return []Diff{
+			Diff{DiffDelete, string(text1)},
+			Diff{DiffInsert, string(text2)},
+		}
+		// Check to see if the problem can be split in two.
+	} else if hm := dmp.diffHalfMatch(text1, text2); hm != nil {
+		// A half-match was found, sort out the return data.
+		text1A := hm[0]
+		text1B := hm[1]
+		text2A := hm[2]
+		text2B := hm[3]
+		midCommon := hm[4]
+		// Send both pairs off for separate processing.
+		diffsA := dmp.diffMainRunes(text1A, text2A, checklines, deadline)
+		diffsB := dmp.diffMainRunes(text1B, text2B, checklines, deadline)
+		// Merge the results.
+		return append(diffsA, append([]Diff{Diff{DiffEqual, string(midCommon)}}, diffsB...)...)
+	} else if checklines && len(text1) > 100 && len(text2) > 100 {
+		return dmp.diffLineMode(text1, text2, deadline)
+	}
+	return dmp.diffBisect(text1, text2, deadline)
+}
+
+// diffLineMode does a quick line-level diff on both []runes, then rediff the parts for greater accuracy. This speedup can produce non-minimal diffs.
+func (dmp *DiffMatchPatch) diffLineMode(text1, text2 []rune, deadline time.Time) []Diff {
+	// Scan the text on a line-by-line basis first.
+	text1, text2, linearray := dmp.diffLinesToRunes(text1, text2)
+
+	diffs := dmp.diffMainRunes(text1, text2, false, deadline)
+
+	// Convert the diff back to original text.
+	diffs = dmp.DiffCharsToLines(diffs, linearray)
+	// Eliminate freak matches (e.g. blank lines)
+	diffs = dmp.DiffCleanupSemantic(diffs)
+
+	// Rediff any replacement blocks, this time character-by-character.
+	// Add a dummy entry at the end.
+	diffs = append(diffs, Diff{DiffEqual, ""})
+
+	pointer := 0
+	countDelete := 0
+	countInsert := 0
+
+	// NOTE: Rune slices are slower than using strings in this case.
+	textDelete := ""
+	textInsert := ""
+
+	for pointer < len(diffs) {
+		switch diffs[pointer].Type {
+		case DiffInsert:
+			countInsert++
+			textInsert += diffs[pointer].Text
+		case DiffDelete:
+			countDelete++
+			textDelete += diffs[pointer].Text
+		case DiffEqual:
+			// Upon reaching an equality, check for prior redundancies.
+			if countDelete >= 1 && countInsert >= 1 {
+				// Delete the offending records and add the merged ones.
+				diffs = splice(diffs, pointer-countDelete-countInsert,
+					countDelete+countInsert)
+
+				pointer = pointer - countDelete - countInsert
+				a := dmp.diffMainRunes([]rune(textDelete), []rune(textInsert), false, deadline)
+				for j := len(a) - 1; j >= 0; j-- {
+					diffs = splice(diffs, pointer, 0, a[j])
+				}
+				pointer = pointer + len(a)
+			}
+
+			countInsert = 0
+			countDelete = 0
+			textDelete = ""
+			textInsert = ""
+		}
+		pointer++
+	}
+
+	return diffs[:len(diffs)-1] // Remove the dummy entry at the end.
+}
+
+// DiffBisect finds the 'middle snake' of a diff, split the problem in two and return the recursively constructed diff.
+// If an invalid UTF-8 sequence is encountered, it will be replaced by the Unicode replacement character.
+// See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
+func (dmp *DiffMatchPatch) DiffBisect(text1, text2 string, deadline time.Time) []Diff {
+	// Unused in this code, but retained for interface compatibility.
+	return dmp.diffBisect([]rune(text1), []rune(text2), deadline)
+}
+
+// diffBisect finds the 'middle snake' of a diff, splits the problem in two and returns the recursively constructed diff.
+// See Myers's 1986 paper: An O(ND) Difference Algorithm and Its Variations.
+func (dmp *DiffMatchPatch) diffBisect(runes1, runes2 []rune, deadline time.Time) []Diff {
+	// Cache the text lengths to prevent multiple calls.
+	runes1Len, runes2Len := len(runes1), len(runes2)
+
+	maxD := (runes1Len + runes2Len + 1) / 2
+	vOffset := maxD
+	vLength := 2 * maxD
+
+	v1 := make([]int, vLength)
+	v2 := make([]int, vLength)
+	for i := range v1 {
+		v1[i] = -1
+		v2[i] = -1
+	}
+	v1[vOffset+1] = 0
+	v2[vOffset+1] = 0
+
+	delta := runes1Len - runes2Len
+	// If the total number of characters is odd, then the front path will collide with the reverse path.
+	front := (delta%2 != 0)
+	// Offsets for start and end of k loop. Prevents mapping of space beyond the grid.
+	k1start := 0
+	k1end := 0
+	k2start := 0
+	k2end := 0
+	for d := 0; d < maxD; d++ {
+		// Bail out if deadline is reached.
+		if !deadline.IsZero() && time.Now().After(deadline) {
+			break
+		}
+
+		// Walk the front path one step.
+		for k1 := -d + k1start; k1 <= d-k1end; k1 += 2 {
+			k1Offset := vOffset + k1
+			var x1 int
+
+			if k1 == -d || (k1 != d && v1[k1Offset-1] < v1[k1Offset+1]) {
+				x1 = v1[k1Offset+1]
+			} else {
+				x1 = v1[k1Offset-1] + 1
+			}
+
+			y1 := x1 - k1
+			for x1 < runes1Len && y1 < runes2Len {
+				if runes1[x1] != runes2[y1] {
+					break
+				}
+				x1++
+				y1++
+			}
+			v1[k1Offset] = x1
+			if x1 > runes1Len {
+				// Ran off the right of the graph.
+				k1end += 2
+			} else if y1 > runes2Len {
+				// Ran off the bottom of the graph.
+				k1start += 2
+			} else if front {
+				k2Offset := vOffset + delta - k1
+				if k2Offset >= 0 && k2Offset < vLength && v2[k2Offset] != -1 {
+					// Mirror x2 onto top-left coordinate system.
+					x2 := runes1Len - v2[k2Offset]
+					if x1 >= x2 {
+						// Overlap detected.
+						return dmp.diffBisectSplit(runes1, runes2, x1, y1, deadline)
+					}
+				}
+			}
+		}
+		// Walk the reverse path one step.
+		for k2 := -d + k2start; k2 <= d-k2end; k2 += 2 {
+			k2Offset := vOffset + k2
+			var x2 int
+			if k2 == -d || (k2 != d && v2[k2Offset-1] < v2[k2Offset+1]) {
+				x2 = v2[k2Offset+1]
+			} else {
+				x2 = v2[k2Offset-1] + 1
+			}
+			var y2 = x2 - k2
+			for x2 < runes1Len && y2 < runes2Len {
+				if runes1[runes1Len-x2-1] != runes2[runes2Len-y2-1] {
+					break
+				}
+				x2++
+				y2++
+			}
+			v2[k2Offset] = x2
+			if x2 > runes1Len {
+				// Ran off the left of the graph.
+				k2end += 2
+			} else if y2 > runes2Len {
+				// Ran off the top of the graph.
+				k2start += 2
+			} else if !front {
+				k1Offset := vOffset + delta - k2
+				if k1Offset >= 0 && k1Offset < vLength && v1[k1Offset] != -1 {
+					x1 := v1[k1Offset]
+					y1 := vOffset + x1 - k1Offset
+					// Mirror x2 onto top-left coordinate system.
+					x2 = runes1Len - x2
+					if x1 >= x2 {
+						// Overlap detected.
+						return dmp.diffBisectSplit(runes1, runes2, x1, y1, deadline)
+					}
+				}
+			}
+		}
+	}
+	// Diff took too long and hit the deadline or number of diffs equals number of characters, no commonality at all.
+	return []Diff{
+		Diff{DiffDelete, string(runes1)},
+		Diff{DiffInsert, string(runes2)},
+	}
+}
+
+func (dmp *DiffMatchPatch) diffBisectSplit(runes1, runes2 []rune, x, y int,
+	deadline time.Time) []Diff {
+	runes1a := runes1[:x]
+	runes2a := runes2[:y]
+	runes1b := runes1[x:]
+	runes2b := runes2[y:]
+
+	// Compute both diffs serially.
+	diffs := dmp.diffMainRunes(runes1a, runes2a, false, deadline)
+	diffsb := dmp.diffMainRunes(runes1b, runes2b, false, deadline)
+
+	return append(diffs, diffsb...)
+}
+
+// DiffLinesToChars splits two texts into a list of strings, and educes the texts to a string of hashes where each Unicode character represents one line.
+// It's slightly faster to call DiffLinesToRunes first, followed by DiffMainRunes.
+func (dmp *DiffMatchPatch) DiffLinesToChars(text1, text2 string) (string, string, []string) {
+	chars1, chars2, lineArray := dmp.DiffLinesToRunes(text1, text2)
+	return string(chars1), string(chars2), lineArray
+}
+
+// DiffLinesToRunes splits two texts into a list of runes. Each rune represents one line.
+func (dmp *DiffMatchPatch) DiffLinesToRunes(text1, text2 string) ([]rune, []rune, []string) {
+	// '\x00' is a valid character, but various debuggers don't like it. So we'll insert a junk entry to avoid generating a null character.
+	lineArray := []string{""}    // e.g. lineArray[4] == 'Hello\n'
+	lineHash := map[string]int{} // e.g. lineHash['Hello\n'] == 4
+
+	chars1 := dmp.diffLinesToRunesMunge(text1, &lineArray, lineHash)
+	chars2 := dmp.diffLinesToRunesMunge(text2, &lineArray, lineHash)
+
+	return chars1, chars2, lineArray
+}
+
+func (dmp *DiffMatchPatch) diffLinesToRunes(text1, text2 []rune) ([]rune, []rune, []string) {
+	return dmp.DiffLinesToRunes(string(text1), string(text2))
+}
+
+// diffLinesToRunesMunge splits a text into an array of strings, and reduces the texts to a []rune where each Unicode character represents one line.
+// We use strings instead of []runes as input mainly because you can't use []rune as a map key.
+func (dmp *DiffMatchPatch) diffLinesToRunesMunge(text string, lineArray *[]string, lineHash map[string]int) []rune {
+	// Walk the text, pulling out a substring for each line. text.split('\n') would would temporarily double our memory footprint. Modifying text would create many large strings to garbage collect.
+	lineStart := 0
+	lineEnd := -1
+	runes := []rune{}
+
+	for lineEnd < len(text)-1 {
+		lineEnd = indexOf(text, "\n", lineStart)
+
+		if lineEnd == -1 {
+			lineEnd = len(text) - 1
+		}
+
+		line := text[lineStart : lineEnd+1]
+		lineStart = lineEnd + 1
+		lineValue, ok := lineHash[line]
+
+		if ok {
+			runes = append(runes, rune(lineValue))
+		} else {
+			*lineArray = append(*lineArray, line)
+			lineHash[line] = len(*lineArray) - 1
+			runes = append(runes, rune(len(*lineArray)-1))
+		}
+	}
+
+	return runes
+}
+
+// DiffCharsToLines rehydrates the text in a diff from a string of line hashes to real lines of text.
+func (dmp *DiffMatchPatch) DiffCharsToLines(diffs []Diff, lineArray []string) []Diff {
+	hydrated := make([]Diff, 0, len(diffs))
+	for _, aDiff := range diffs {
+		chars := aDiff.Text
+		text := make([]string, len(chars))
+
+		for i, r := range chars {
+			text[i] = lineArray[r]
+		}
+
+		aDiff.Text = strings.Join(text, "")
+		hydrated = append(hydrated, aDiff)
+	}
+	return hydrated
+}
+
+// DiffCommonPrefix determines the common prefix length of two strings.
+func (dmp *DiffMatchPatch) DiffCommonPrefix(text1, text2 string) int {
+	// Unused in this code, but retained for interface compatibility.
+	return commonPrefixLength([]rune(text1), []rune(text2))
+}
+
+// DiffCommonSuffix determines the common suffix length of two strings.
+func (dmp *DiffMatchPatch) DiffCommonSuffix(text1, text2 string) int {
+	// Unused in this code, but retained for interface compatibility.
+	return commonSuffixLength([]rune(text1), []rune(text2))
+}
+
+// commonPrefixLength returns the length of the common prefix of two rune slices.
+func commonPrefixLength(text1, text2 []rune) int {
+	short, long := text1, text2
+	if len(short) > len(long) {
+		short, long = long, short
+	}
+	for i, r := range short {
+		if r != long[i] {
+			return i
+		}
+	}
+	return len(short)
+}
+
+// commonSuffixLength returns the length of the common suffix of two rune slices.
+func commonSuffixLength(text1, text2 []rune) int {
+	n := min(len(text1), len(text2))
+	for i := 0; i < n; i++ {
+		if text1[len(text1)-i-1] != text2[len(text2)-i-1] {
+			return i
+		}
+	}
+	return n
+
+	// TODO research and benchmark this, why is it not activated? https://github.com/sergi/go-diff/issues/54
+	// Binary search.
+	// Performance analysis: http://neil.fraser.name/news/2007/10/09/
+	/*
+	   pointermin := 0
+	   pointermax := math.Min(len(text1), len(text2))
+	   pointermid := pointermax
+	   pointerend := 0
+	   for pointermin < pointermid {
+	       if text1[len(text1)-pointermid:len(text1)-pointerend] ==
+	           text2[len(text2)-pointermid:len(text2)-pointerend] {
+	           pointermin = pointermid
+	           pointerend = pointermin
+	       } else {
+	           pointermax = pointermid
+	       }
+	       pointermid = math.Floor((pointermax-pointermin)/2 + pointermin)
+	   }
+	   return pointermid
+	*/
+}
+
+// DiffCommonOverlap determines if the suffix of one string is the prefix of another.
+func (dmp *DiffMatchPatch) DiffCommonOverlap(text1 string, text2 string) int {
+	// Cache the text lengths to prevent multiple calls.
+	text1Length := len(text1)
+	text2Length := len(text2)
+	// Eliminate the null case.
+	if text1Length == 0 || text2Length == 0 {
+		return 0
+	}
+	// Truncate the longer string.
+	if text1Length > text2Length {
+		text1 = text1[text1Length-text2Length:]
+	} else if text1Length < text2Length {
+		text2 = text2[0:text1Length]
+	}
+	textLength := int(math.Min(float64(text1Length), float64(text2Length)))
+	// Quick check for the worst case.
+	if text1 == text2 {
+		return textLength
+	}
+
+	// Start by looking for a single character match and increase length until no match is found. Performance analysis: http://neil.fraser.name/news/2010/11/04/
+	best := 0
+	length := 1
+	for {
+		pattern := text1[textLength-length:]
+		found := strings.Index(text2, pattern)
+		if found == -1 {
+			break
+		}
+		length += found
+		if found == 0 || text1[textLength-length:] == text2[0:length] {
+			best = length
+			length++
+		}
+	}
+
+	return best
+}
+
+// DiffHalfMatch checks whether the two texts share a substring which is at least half the length of the longer text. This speedup can produce non-minimal diffs.
+func (dmp *DiffMatchPatch) DiffHalfMatch(text1, text2 string) []string {
+	// Unused in this code, but retained for interface compatibility.
+	runeSlices := dmp.diffHalfMatch([]rune(text1), []rune(text2))
+	if runeSlices == nil {
+		return nil
+	}
+
+	result := make([]string, len(runeSlices))
+	for i, r := range runeSlices {
+		result[i] = string(r)
+	}
+	return result
+}
+
+func (dmp *DiffMatchPatch) diffHalfMatch(text1, text2 []rune) [][]rune {
+	if dmp.DiffTimeout <= 0 {
+		// Don't risk returning a non-optimal diff if we have unlimited time.
+		return nil
+	}
+
+	var longtext, shorttext []rune
+	if len(text1) > len(text2) {
+		longtext = text1
+		shorttext = text2
+	} else {
+		longtext = text2
+		shorttext = text1
+	}
+
+	if len(longtext) < 4 || len(shorttext)*2 < len(longtext) {
+		return nil // Pointless.
+	}
+
+	// First check if the second quarter is the seed for a half-match.
+	hm1 := dmp.diffHalfMatchI(longtext, shorttext, int(float64(len(longtext)+3)/4))
+
+	// Check again based on the third quarter.
+	hm2 := dmp.diffHalfMatchI(longtext, shorttext, int(float64(len(longtext)+1)/2))
+
+	hm := [][]rune{}
+	if hm1 == nil && hm2 == nil {
+		return nil
+	} else if hm2 == nil {
+		hm = hm1
+	} else if hm1 == nil {
+		hm = hm2
+	} else {
+		// Both matched.  Select the longest.
+		if len(hm1[4]) > len(hm2[4]) {
+			hm = hm1
+		} else {
+			hm = hm2
+		}
+	}
+
+	// A half-match was found, sort out the return data.
+	if len(text1) > len(text2) {
+		return hm
+	}
+
+	return [][]rune{hm[2], hm[3], hm[0], hm[1], hm[4]}
+}
+
+// diffHalfMatchI checks if a substring of shorttext exist within longtext such that the substring is at least half the length of longtext?
+// Returns a slice containing the prefix of longtext, the suffix of longtext, the prefix of shorttext, the suffix of shorttext and the common middle, or null if there was no match.
+func (dmp *DiffMatchPatch) diffHalfMatchI(l, s []rune, i int) [][]rune {
+	var bestCommonA []rune
+	var bestCommonB []rune
+	var bestCommonLen int
+	var bestLongtextA []rune
+	var bestLongtextB []rune
+	var bestShorttextA []rune
+	var bestShorttextB []rune
+
+	// Start with a 1/4 length substring at position i as a seed.
+	seed := l[i : i+len(l)/4]
+
+	for j := runesIndexOf(s, seed, 0); j != -1; j = runesIndexOf(s, seed, j+1) {
+		prefixLength := commonPrefixLength(l[i:], s[j:])
+		suffixLength := commonSuffixLength(l[:i], s[:j])
+
+		if bestCommonLen < suffixLength+prefixLength {
+			bestCommonA = s[j-suffixLength : j]
+			bestCommonB = s[j : j+prefixLength]
+			bestCommonLen = len(bestCommonA) + len(bestCommonB)
+			bestLongtextA = l[:i-suffixLength]
+			bestLongtextB = l[i+prefixLength:]
+			bestShorttextA = s[:j-suffixLength]
+			bestShorttextB = s[j+prefixLength:]
+		}
+	}
+
+	if bestCommonLen*2 < len(l) {
+		return nil
+	}
+
+	return [][]rune{
+		bestLongtextA,
+		bestLongtextB,
+		bestShorttextA,
+		bestShorttextB,
+		append(bestCommonA, bestCommonB...),
+	}
+}
+
+// DiffCleanupSemantic reduces the number of edits by eliminating semantically trivial equalities.
+func (dmp *DiffMatchPatch) DiffCleanupSemantic(diffs []Diff) []Diff {
+	changes := false
+	// Stack of indices where equalities are found.
+	type equality struct {
+		data int
+		next *equality
+	}
+	var equalities *equality
+
+	var lastequality string
+	// Always equal to diffs[equalities[equalitiesLength - 1]][1]
+	var pointer int // Index of current position.
+	// Number of characters that changed prior to the equality.
+	var lengthInsertions1, lengthDeletions1 int
+	// Number of characters that changed after the equality.
+	var lengthInsertions2, lengthDeletions2 int
+
+	for pointer < len(diffs) {
+		if diffs[pointer].Type == DiffEqual {
+			// Equality found.
+
+			equalities = &equality{
+				data: pointer,
+				next: equalities,
+			}
+			lengthInsertions1 = lengthInsertions2
+			lengthDeletions1 = lengthDeletions2
+			lengthInsertions2 = 0
+			lengthDeletions2 = 0
+			lastequality = diffs[pointer].Text
+		} else {
+			// An insertion or deletion.
+
+			if diffs[pointer].Type == DiffInsert {
+				lengthInsertions2 += len(diffs[pointer].Text)
+			} else {
+				lengthDeletions2 += len(diffs[pointer].Text)
+			}
+			// Eliminate an equality that is smaller or equal to the edits on both sides of it.
+			difference1 := int(math.Max(float64(lengthInsertions1), float64(lengthDeletions1)))
+			difference2 := int(math.Max(float64(lengthInsertions2), float64(lengthDeletions2)))
+			if len(lastequality) > 0 &&
+				(len(lastequality) <= difference1) &&
+				(len(lastequality) <= difference2) {
+				// Duplicate record.
+				insPoint := equalities.data
+				diffs = append(
+					diffs[:insPoint],
+					append([]Diff{Diff{DiffDelete, lastequality}}, diffs[insPoint:]...)...)
+
+				// Change second copy to insert.
+				diffs[insPoint+1].Type = DiffInsert
+				// Throw away the equality we just deleted.
+				equalities = equalities.next
+
+				if equalities != nil {
+					equalities = equalities.next
+				}
+				if equalities != nil {
+					pointer = equalities.data
+				} else {
+					pointer = -1
+				}
+
+				lengthInsertions1 = 0 // Reset the counters.
+				lengthDeletions1 = 0
+				lengthInsertions2 = 0
+				lengthDeletions2 = 0
+				lastequality = ""
+				changes = true
+			}
+		}
+		pointer++
+	}
+
+	// Normalize the diff.
+	if changes {
+		diffs = dmp.DiffCleanupMerge(diffs)
+	}
+	diffs = dmp.DiffCleanupSemanticLossless(diffs)
+	// Find any overlaps between deletions and insertions.
+	// e.g: <del>abcxxx</del><ins>xxxdef</ins>
+	//   -> <del>abc</del>xxx<ins>def</ins>
+	// e.g: <del>xxxabc</del><ins>defxxx</ins>
+	//   -> <ins>def</ins>xxx<del>abc</del>
+	// Only extract an overlap if it is as big as the edit ahead or behind it.
+	pointer = 1
+	for pointer < len(diffs) {
+		if diffs[pointer-1].Type == DiffDelete &&
+			diffs[pointer].Type == DiffInsert {
+			deletion := diffs[pointer-1].Text
+			insertion := diffs[pointer].Text
+			overlapLength1 := dmp.DiffCommonOverlap(deletion, insertion)
+			overlapLength2 := dmp.DiffCommonOverlap(insertion, deletion)
+			if overlapLength1 >= overlapLength2 {
+				if float64(overlapLength1) >= float64(len(deletion))/2 ||
+					float64(overlapLength1) >= float64(len(insertion))/2 {
+
+					// Overlap found. Insert an equality and trim the surrounding edits.
+					diffs = append(
+						diffs[:pointer],
+						append([]Diff{Diff{DiffEqual, insertion[:overlapLength1]}}, diffs[pointer:]...)...)
+
+					diffs[pointer-1].Text =
+						deletion[0 : len(deletion)-overlapLength1]
+					diffs[pointer+1].Text = insertion[overlapLength1:]
+					pointer++
+				}
+			} else {
+				if float64(overlapLength2) >= float64(len(deletion))/2 ||
+					float64(overlapLength2) >= float64(len(insertion))/2 {
+					// Reverse overlap found. Insert an equality and swap and trim the surrounding edits.
+					overlap := Diff{DiffEqual, deletion[:overlapLength2]}
+					diffs = append(
+						diffs[:pointer],
+						append([]Diff{overlap}, diffs[pointer:]...)...)
+
+					diffs[pointer-1].Type = DiffInsert
+					diffs[pointer-1].Text = insertion[0 : len(insertion)-overlapLength2]
+					diffs[pointer+1].Type = DiffDelete
+					diffs[pointer+1].Text = deletion[overlapLength2:]
+					pointer++
+				}
+			}
+			pointer++
+		}
+		pointer++
+	}
+
+	return diffs
+}
+
+// Define some regex patterns for matching boundaries.
+var (
+	nonAlphaNumericRegex = regexp.MustCompile(`[^a-zA-Z0-9]`)
+	whitespaceRegex      = regexp.MustCompile(`\s`)
+	linebreakRegex       = regexp.MustCompile(`[\r\n]`)
+	blanklineEndRegex    = regexp.MustCompile(`\n\r?\n$`)
+	blanklineStartRegex  = regexp.MustCompile(`^\r?\n\r?\n`)
+)
+
+// diffCleanupSemanticScore computes a score representing whether the internal boundary falls on logical boundaries.
+// Scores range from 6 (best) to 0 (worst). Closure, but does not reference any external variables.
+func diffCleanupSemanticScore(one, two string) int {
+	if len(one) == 0 || len(two) == 0 {
+		// Edges are the best.
+		return 6
+	}
+
+	// Each port of this function behaves slightly differently due to subtle differences in each language's definition of things like 'whitespace'.  Since this function's purpose is largely cosmetic, the choice has been made to use each language's native features rather than force total conformity.
+	rune1, _ := utf8.DecodeLastRuneInString(one)
+	rune2, _ := utf8.DecodeRuneInString(two)
+	char1 := string(rune1)
+	char2 := string(rune2)
+
+	nonAlphaNumeric1 := nonAlphaNumericRegex.MatchString(char1)
+	nonAlphaNumeric2 := nonAlphaNumericRegex.MatchString(char2)
+	whitespace1 := nonAlphaNumeric1 && whitespaceRegex.MatchString(char1)
+	whitespace2 := nonAlphaNumeric2 && whitespaceRegex.MatchString(char2)
+	lineBreak1 := whitespace1 && linebreakRegex.MatchString(char1)
+	lineBreak2 := whitespace2 && linebreakRegex.MatchString(char2)
+	blankLine1 := lineBreak1 && blanklineEndRegex.MatchString(one)
+	blankLine2 := lineBreak2 && blanklineEndRegex.MatchString(two)
+
+	if blankLine1 || blankLine2 {
+		// Five points for blank lines.
+		return 5
+	} else if lineBreak1 || lineBreak2 {
+		// Four points for line breaks.
+		return 4
+	} else if nonAlphaNumeric1 && !whitespace1 && whitespace2 {
+		// Three points for end of sentences.
+		return 3
+	} else if whitespace1 || whitespace2 {
+		// Two points for whitespace.
+		return 2
+	} else if nonAlphaNumeric1 || nonAlphaNumeric2 {
+		// One point for non-alphanumeric.
+		return 1
+	}
+	return 0
+}
+
+// DiffCleanupSemanticLossless looks for single edits surrounded on both sides by equalities which can be shifted sideways to align the edit to a word boundary.
+// E.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
+func (dmp *DiffMatchPatch) DiffCleanupSemanticLossless(diffs []Diff) []Diff {
+	pointer := 1
+
+	// Intentionally ignore the first and last element (don't need checking).
+	for pointer < len(diffs)-1 {
+		if diffs[pointer-1].Type == DiffEqual &&
+			diffs[pointer+1].Type == DiffEqual {
+
+			// This is a single edit surrounded by equalities.
+			equality1 := diffs[pointer-1].Text
+			edit := diffs[pointer].Text
+			equality2 := diffs[pointer+1].Text
+
+			// First, shift the edit as far left as possible.
+			commonOffset := dmp.DiffCommonSuffix(equality1, edit)
+			if commonOffset > 0 {
+				commonString := edit[len(edit)-commonOffset:]
+				equality1 = equality1[0 : len(equality1)-commonOffset]
+				edit = commonString + edit[:len(edit)-commonOffset]
+				equality2 = commonString + equality2
+			}
+
+			// Second, step character by character right, looking for the best fit.
+			bestEquality1 := equality1
+			bestEdit := edit
+			bestEquality2 := equality2
+			bestScore := diffCleanupSemanticScore(equality1, edit) +
+				diffCleanupSemanticScore(edit, equality2)
+
+			for len(edit) != 0 && len(equality2) != 0 {
+				_, sz := utf8.DecodeRuneInString(edit)
+				if len(equality2) < sz || edit[:sz] != equality2[:sz] {
+					break
+				}
+				equality1 += edit[:sz]
+				edit = edit[sz:] + equality2[:sz]
+				equality2 = equality2[sz:]
+				score := diffCleanupSemanticScore(equality1, edit) +
+					diffCleanupSemanticScore(edit, equality2)
+				// The >= encourages trailing rather than leading whitespace on edits.
+				if score >= bestScore {
+					bestScore = score
+					bestEquality1 = equality1
+					bestEdit = edit
+					bestEquality2 = equality2
+				}
+			}
+
+			if diffs[pointer-1].Text != bestEquality1 {
+				// We have an improvement, save it back to the diff.
+				if len(bestEquality1) != 0 {
+					diffs[pointer-1].Text = bestEquality1
+				} else {
+					diffs = splice(diffs, pointer-1, 1)
+					pointer--
+				}
+
+				diffs[pointer].Text = bestEdit
+				if len(bestEquality2) != 0 {
+					diffs[pointer+1].Text = bestEquality2
+				} else {
+					diffs = append(diffs[:pointer+1], diffs[pointer+2:]...)
+					pointer--
+				}
+			}
+		}
+		pointer++
+	}
+
+	return diffs
+}
+
+// DiffCleanupEfficiency reduces the number of edits by eliminating operationally trivial equalities.
+func (dmp *DiffMatchPatch) DiffCleanupEfficiency(diffs []Diff) []Diff {
+	changes := false
+	// Stack of indices where equalities are found.
+	type equality struct {
+		data int
+		next *equality
+	}
+	var equalities *equality
+	// Always equal to equalities[equalitiesLength-1][1]
+	lastequality := ""
+	pointer := 0 // Index of current position.
+	// Is there an insertion operation before the last equality.
+	preIns := false
+	// Is there a deletion operation before the last equality.
+	preDel := false
+	// Is there an insertion operation after the last equality.
+	postIns := false
+	// Is there a deletion operation after the last equality.
+	postDel := false
+	for pointer < len(diffs) {
+		if diffs[pointer].Type == DiffEqual { // Equality found.
+			if len(diffs[pointer].Text) < dmp.DiffEditCost &&
+				(postIns || postDel) {
+				// Candidate found.
+				equalities = &equality{
+					data: pointer,
+					next: equalities,
+				}
+				preIns = postIns
+				preDel = postDel
+				lastequality = diffs[pointer].Text
+			} else {
+				// Not a candidate, and can never become one.
+				equalities = nil
+				lastequality = ""
+			}
+			postIns = false
+			postDel = false
+		} else { // An insertion or deletion.
+			if diffs[pointer].Type == DiffDelete {
+				postDel = true
+			} else {
+				postIns = true
+			}
+
+			// Five types to be split:
+			// <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
+			// <ins>A</ins>X<ins>C</ins><del>D</del>
+			// <ins>A</ins><del>B</del>X<ins>C</ins>
+			// <ins>A</del>X<ins>C</ins><del>D</del>
+			// <ins>A</ins><del>B</del>X<del>C</del>
+			var sumPres int
+			if preIns {
+				sumPres++
+			}
+			if preDel {
+				sumPres++
+			}
+			if postIns {
+				sumPres++
+			}
+			if postDel {
+				sumPres++
+			}
+			if len(lastequality) > 0 &&
+				((preIns && preDel && postIns && postDel) ||
+					((len(lastequality) < dmp.DiffEditCost/2) && sumPres == 3)) {
+
+				insPoint := equalities.data
+
+				// Duplicate record.
+				diffs = append(diffs[:insPoint],
+					append([]Diff{Diff{DiffDelete, lastequality}}, diffs[insPoint:]...)...)
+
+				// Change second copy to insert.
+				diffs[insPoint+1].Type = DiffInsert
+				// Throw away the equality we just deleted.
+				equalities = equalities.next
+				lastequality = ""
+
+				if preIns && preDel {
+					// No changes made which could affect previous entry, keep going.
+					postIns = true
+					postDel = true
+					equalities = nil
+				} else {
+					if equalities != nil {
+						equalities = equalities.next
+					}
+					if equalities != nil {
+						pointer = equalities.data
+					} else {
+						pointer = -1
+					}
+					postIns = false
+					postDel = false
+				}
+				changes = true
+			}
+		}
+		pointer++
+	}
+
+	if changes {
+		diffs = dmp.DiffCleanupMerge(diffs)
+	}
+
+	return diffs
+}
+
+// DiffCleanupMerge reorders and merges like edit sections. Merge equalities.
+// Any edit section can move as long as it doesn't cross an equality.
+func (dmp *DiffMatchPatch) DiffCleanupMerge(diffs []Diff) []Diff {
+	// Add a dummy entry at the end.
+	diffs = append(diffs, Diff{DiffEqual, ""})
+	pointer := 0
+	countDelete := 0
+	countInsert := 0
+	commonlength := 0
+	textDelete := []rune(nil)
+	textInsert := []rune(nil)
+
+	for pointer < len(diffs) {
+		switch diffs[pointer].Type {
+		case DiffInsert:
+			countInsert++
+			textInsert = append(textInsert, []rune(diffs[pointer].Text)...)
+			pointer++
+			break
+		case DiffDelete:
+			countDelete++
+			textDelete = append(textDelete, []rune(diffs[pointer].Text)...)
+			pointer++
+			break
+		case DiffEqual:
+			// Upon reaching an equality, check for prior redundancies.
+			if countDelete+countInsert > 1 {
+				if countDelete != 0 && countInsert != 0 {
+					// Factor out any common prefixies.
+					commonlength = commonPrefixLength(textInsert, textDelete)
+					if commonlength != 0 {
+						x := pointer - countDelete - countInsert
+						if x > 0 && diffs[x-1].Type == DiffEqual {
+							diffs[x-1].Text += string(textInsert[:commonlength])
+						} else {
+							diffs = append([]Diff{Diff{DiffEqual, string(textInsert[:commonlength])}}, diffs...)
+							pointer++
+						}
+						textInsert = textInsert[commonlength:]
+						textDelete = textDelete[commonlength:]
+					}
+					// Factor out any common suffixies.
+					commonlength = commonSuffixLength(textInsert, textDelete)
+					if commonlength != 0 {
+						insertIndex := len(textInsert) - commonlength
+						deleteIndex := len(textDelete) - commonlength
+						diffs[pointer].Text = string(textInsert[insertIndex:]) + diffs[pointer].Text
+						textInsert = textInsert[:insertIndex]
+						textDelete = textDelete[:deleteIndex]
+					}
+				}
+				// Delete the offending records and add the merged ones.
+				if countDelete == 0 {
+					diffs = splice(diffs, pointer-countInsert,
+						countDelete+countInsert,
+						Diff{DiffInsert, string(textInsert)})
+				} else if countInsert == 0 {
+					diffs = splice(diffs, pointer-countDelete,
+						countDelete+countInsert,
+						Diff{DiffDelete, string(textDelete)})
+				} else {
+					diffs = splice(diffs, pointer-countDelete-countInsert,
+						countDelete+countInsert,
+						Diff{DiffDelete, string(textDelete)},
+						Diff{DiffInsert, string(textInsert)})
+				}
+
+				pointer = pointer - countDelete - countInsert + 1
+				if countDelete != 0 {
+					pointer++
+				}
+				if countInsert != 0 {
+					pointer++
+				}
+			} else if pointer != 0 && diffs[pointer-1].Type == DiffEqual {
+				// Merge this equality with the previous one.
+				diffs[pointer-1].Text += diffs[pointer].Text
+				diffs = append(diffs[:pointer], diffs[pointer+1:]...)
+			} else {
+				pointer++
+			}
+			countInsert = 0
+			countDelete = 0
+			textDelete = nil
+			textInsert = nil
+			break
+		}
+	}
+
+	if len(diffs[len(diffs)-1].Text) == 0 {
+		diffs = diffs[0 : len(diffs)-1] // Remove the dummy entry at the end.
+	}
+
+	// Second pass: look for single edits surrounded on both sides by equalities which can be shifted sideways to eliminate an equality. E.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
+	changes := false
+	pointer = 1
+	// Intentionally ignore the first and last element (don't need checking).
+	for pointer < (len(diffs) - 1) {
+		if diffs[pointer-1].Type == DiffEqual &&
+			diffs[pointer+1].Type == DiffEqual {
+			// This is a single edit surrounded by equalities.
+			if strings.HasSuffix(diffs[pointer].Text, diffs[pointer-1].Text) {
+				// Shift the edit over the previous equality.
+				diffs[pointer].Text = diffs[pointer-1].Text +
+					diffs[pointer].Text[:len(diffs[pointer].Text)-len(diffs[pointer-1].Text)]
+				diffs[pointer+1].Text = diffs[pointer-1].Text + diffs[pointer+1].Text
+				diffs = splice(diffs, pointer-1, 1)
+				changes = true
+			} else if strings.HasPrefix(diffs[pointer].Text, diffs[pointer+1].Text) {
+				// Shift the edit over the next equality.
+				diffs[pointer-1].Text += diffs[pointer+1].Text
+				diffs[pointer].Text =
+					diffs[pointer].Text[len(diffs[pointer+1].Text):] + diffs[pointer+1].Text
+				diffs = splice(diffs, pointer+1, 1)
+				changes = true
+			}
+		}
+		pointer++
+	}
+
+	// If shifts were made, the diff needs reordering and another shift sweep.
+	if changes {
+		diffs = dmp.DiffCleanupMerge(diffs)
+	}
+
+	return diffs
+}
+
+// DiffXIndex returns the equivalent location in s2.
+func (dmp *DiffMatchPatch) DiffXIndex(diffs []Diff, loc int) int {
+	chars1 := 0
+	chars2 := 0
+	lastChars1 := 0
+	lastChars2 := 0
+	lastDiff := Diff{}
+	for i := 0; i < len(diffs); i++ {
+		aDiff := diffs[i]
+		if aDiff.Type != DiffInsert {
+			// Equality or deletion.
+			chars1 += len(aDiff.Text)
+		}
+		if aDiff.Type != DiffDelete {
+			// Equality or insertion.
+			chars2 += len(aDiff.Text)
+		}
+		if chars1 > loc {
+			// Overshot the location.
+			lastDiff = aDiff
+			break
+		}
+		lastChars1 = chars1
+		lastChars2 = chars2
+	}
+	if lastDiff.Type == DiffDelete {
+		// The location was deleted.
+		return lastChars2
+	}
+	// Add the remaining character length.
+	return lastChars2 + (loc - lastChars1)
+}
+
+// DiffPrettyHtml converts a []Diff into a pretty HTML report.
+// It is intended as an example from which to write one's own display functions.
+func (dmp *DiffMatchPatch) DiffPrettyHtml(diffs []Diff) string {
+	var buff bytes.Buffer
+	for _, diff := range diffs {
+		text := strings.Replace(html.EscapeString(diff.Text), "\n", "&para;<br>", -1)
+		switch diff.Type {
+		case DiffInsert:
+			_, _ = buff.WriteString("<ins style=\"background:#e6ffe6;\">")
+			_, _ = buff.WriteString(text)
+			_, _ = buff.WriteString("</ins>")
+		case DiffDelete:
+			_, _ = buff.WriteString("<del style=\"background:#ffe6e6;\">")
+			_, _ = buff.WriteString(text)
+			_, _ = buff.WriteString("</del>")
+		case DiffEqual:
+			_, _ = buff.WriteString("<span>")
+			_, _ = buff.WriteString(text)
+			_, _ = buff.WriteString("</span>")
+		}
+	}
+	return buff.String()
+}
+
+// DiffPrettyText converts a []Diff into a colored text report.
+func (dmp *DiffMatchPatch) DiffPrettyText(diffs []Diff) string {
+	var buff bytes.Buffer
+	for _, diff := range diffs {
+		text := diff.Text
+
+		switch diff.Type {
+		case DiffInsert:
+			_, _ = buff.WriteString("\x1b[32m")
+			_, _ = buff.WriteString(text)
+			_, _ = buff.WriteString("\x1b[0m")
+		case DiffDelete:
+			_, _ = buff.WriteString("\x1b[31m")
+			_, _ = buff.WriteString(text)
+			_, _ = buff.WriteString("\x1b[0m")
+		case DiffEqual:
+			_, _ = buff.WriteString(text)
+		}
+	}
+
+	return buff.String()
+}
+
+// DiffText1 computes and returns the source text (all equalities and deletions).
+func (dmp *DiffMatchPatch) DiffText1(diffs []Diff) string {
+	//StringBuilder text = new StringBuilder()
+	var text bytes.Buffer
+
+	for _, aDiff := range diffs {
+		if aDiff.Type != DiffInsert {
+			_, _ = text.WriteString(aDiff.Text)
+		}
+	}
+	return text.String()
+}
+
+// DiffText2 computes and returns the destination text (all equalities and insertions).
+func (dmp *DiffMatchPatch) DiffText2(diffs []Diff) string {
+	var text bytes.Buffer
+
+	for _, aDiff := range diffs {
+		if aDiff.Type != DiffDelete {
+			_, _ = text.WriteString(aDiff.Text)
+		}
+	}
+	return text.String()
+}
+
+// DiffLevenshtein computes the Levenshtein distance that is the number of inserted, deleted or substituted characters.
+func (dmp *DiffMatchPatch) DiffLevenshtein(diffs []Diff) int {
+	levenshtein := 0
+	insertions := 0
+	deletions := 0
+
+	for _, aDiff := range diffs {
+		switch aDiff.Type {
+		case DiffInsert:
+			insertions += len(aDiff.Text)
+		case DiffDelete:
+			deletions += len(aDiff.Text)
+		case DiffEqual:
+			// A deletion and an insertion is one substitution.
+			levenshtein += max(insertions, deletions)
+			insertions = 0
+			deletions = 0
+		}
+	}
+
+	levenshtein += max(insertions, deletions)
+	return levenshtein
+}
+
+// DiffToDelta crushes the diff into an encoded string which describes the operations required to transform text1 into text2.
+// E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'. Operations are tab-separated.  Inserted text is escaped using %xx notation.
+func (dmp *DiffMatchPatch) DiffToDelta(diffs []Diff) string {
+	var text bytes.Buffer
+	for _, aDiff := range diffs {
+		switch aDiff.Type {
+		case DiffInsert:
+			_, _ = text.WriteString("+")
+			_, _ = text.WriteString(strings.Replace(url.QueryEscape(aDiff.Text), "+", " ", -1))
+			_, _ = text.WriteString("\t")
+			break
+		case DiffDelete:
+			_, _ = text.WriteString("-")
+			_, _ = text.WriteString(strconv.Itoa(utf8.RuneCountInString(aDiff.Text)))
+			_, _ = text.WriteString("\t")
+			break
+		case DiffEqual:
+			_, _ = text.WriteString("=")
+			_, _ = text.WriteString(strconv.Itoa(utf8.RuneCountInString(aDiff.Text)))
+			_, _ = text.WriteString("\t")
+			break
+		}
+	}
+	delta := text.String()
+	if len(delta) != 0 {
+		// Strip off trailing tab character.
+		delta = delta[0 : utf8.RuneCountInString(delta)-1]
+		delta = unescaper.Replace(delta)
+	}
+	return delta
+}
+
+// DiffFromDelta given the original text1, and an encoded string which describes the operations required to transform text1 into text2, comAdde the full diff.
+func (dmp *DiffMatchPatch) DiffFromDelta(text1 string, delta string) (diffs []Diff, err error) {
+	i := 0
+	runes := []rune(text1)
+
+	for _, token := range strings.Split(delta, "\t") {
+		if len(token) == 0 {
+			// Blank tokens are ok (from a trailing \t).
+			continue
+		}
+
+		// Each token begins with a one character parameter which specifies the operation of this token (delete, insert, equality).
+		param := token[1:]
+
+		switch op := token[0]; op {
+		case '+':
+			// Decode would Diff all "+" to " "
+			param = strings.Replace(param, "+", "%2b", -1)
+			param, err = url.QueryUnescape(param)
+			if err != nil {
+				return nil, err
+			}
+			if !utf8.ValidString(param) {
+				return nil, fmt.Errorf("invalid UTF-8 token: %q", param)
+			}
+
+			diffs = append(diffs, Diff{DiffInsert, param})
+		case '=', '-':
+			n, err := strconv.ParseInt(param, 10, 0)
+			if err != nil {
+				return nil, err
+			} else if n < 0 {
+				return nil, errors.New("Negative number in DiffFromDelta: " + param)
+			}
+
+			i += int(n)
+			// Break out if we are out of bounds, go1.6 can't handle this very well
+			if i > len(runes) {
+				break
+			}
+			// Remember that string slicing is by byte - we want by rune here.
+			text := string(runes[i-int(n) : i])
+
+			if op == '=' {
+				diffs = append(diffs, Diff{DiffEqual, text})
+			} else {
+				diffs = append(diffs, Diff{DiffDelete, text})
+			}
+		default:
+			// Anything else is an error.
+			return nil, errors.New("Invalid diff operation in DiffFromDelta: " + string(token[0]))
+		}
+	}
+
+	if i != len(runes) {
+		return nil, fmt.Errorf("Delta length (%v) is different from source text length (%v)", i, len(text1))
+	}
+
+	return diffs, nil
+}
diff --git a/vendor/github.com/sergi/go-diff/diffmatchpatch/diffmatchpatch.go b/vendor/github.com/sergi/go-diff/diffmatchpatch/diffmatchpatch.go
new file mode 100644
index 00000000..d3acc32c
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/diffmatchpatch/diffmatchpatch.go
@@ -0,0 +1,46 @@
+// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
+// https://github.com/sergi/go-diff
+// See the included LICENSE file for license details.
+//
+// go-diff is a Go implementation of Google's Diff, Match, and Patch library
+// Original library is Copyright (c) 2006 Google Inc.
+// http://code.google.com/p/google-diff-match-patch/
+
+// Package diffmatchpatch offers robust algorithms to perform the operations required for synchronizing plain text.
+package diffmatchpatch
+
+import (
+	"time"
+)
+
+// DiffMatchPatch holds the configuration for diff-match-patch operations.
+type DiffMatchPatch struct {
+	// Number of seconds to map a diff before giving up (0 for infinity).
+	DiffTimeout time.Duration
+	// Cost of an empty edit operation in terms of edit characters.
+	DiffEditCost int
+	// How far to search for a match (0 = exact location, 1000+ = broad match). A match this many characters away from the expected location will add 1.0 to the score (0.0 is a perfect match).
+	MatchDistance int
+	// When deleting a large block of text (over ~64 characters), how close do the contents have to be to match the expected contents. (0.0 = perfection, 1.0 = very loose).  Note that MatchThreshold controls how closely the end points of a delete need to match.
+	PatchDeleteThreshold float64
+	// Chunk size for context length.
+	PatchMargin int
+	// The number of bits in an int.
+	MatchMaxBits int
+	// At what point is no match declared (0.0 = perfection, 1.0 = very loose).
+	MatchThreshold float64
+}
+
+// New creates a new DiffMatchPatch object with default parameters.
+func New() *DiffMatchPatch {
+	// Defaults.
+	return &DiffMatchPatch{
+		DiffTimeout:          time.Second,
+		DiffEditCost:         4,
+		MatchThreshold:       0.5,
+		MatchDistance:        1000,
+		PatchDeleteThreshold: 0.5,
+		PatchMargin:          4,
+		MatchMaxBits:         32,
+	}
+}
diff --git a/vendor/github.com/sergi/go-diff/diffmatchpatch/match.go b/vendor/github.com/sergi/go-diff/diffmatchpatch/match.go
new file mode 100644
index 00000000..17374e10
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/diffmatchpatch/match.go
@@ -0,0 +1,160 @@
+// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
+// https://github.com/sergi/go-diff
+// See the included LICENSE file for license details.
+//
+// go-diff is a Go implementation of Google's Diff, Match, and Patch library
+// Original library is Copyright (c) 2006 Google Inc.
+// http://code.google.com/p/google-diff-match-patch/
+
+package diffmatchpatch
+
+import (
+	"math"
+)
+
+// MatchMain locates the best instance of 'pattern' in 'text' near 'loc'.
+// Returns -1 if no match found.
+func (dmp *DiffMatchPatch) MatchMain(text, pattern string, loc int) int {
+	// Check for null inputs not needed since null can't be passed in C#.
+
+	loc = int(math.Max(0, math.Min(float64(loc), float64(len(text)))))
+	if text == pattern {
+		// Shortcut (potentially not guaranteed by the algorithm)
+		return 0
+	} else if len(text) == 0 {
+		// Nothing to match.
+		return -1
+	} else if loc+len(pattern) <= len(text) && text[loc:loc+len(pattern)] == pattern {
+		// Perfect match at the perfect spot!  (Includes case of null pattern)
+		return loc
+	}
+	// Do a fuzzy compare.
+	return dmp.MatchBitap(text, pattern, loc)
+}
+
+// MatchBitap locates the best instance of 'pattern' in 'text' near 'loc' using the Bitap algorithm.
+// Returns -1 if no match was found.
+func (dmp *DiffMatchPatch) MatchBitap(text, pattern string, loc int) int {
+	// Initialise the alphabet.
+	s := dmp.MatchAlphabet(pattern)
+
+	// Highest score beyond which we give up.
+	scoreThreshold := dmp.MatchThreshold
+	// Is there a nearby exact match? (speedup)
+	bestLoc := indexOf(text, pattern, loc)
+	if bestLoc != -1 {
+		scoreThreshold = math.Min(dmp.matchBitapScore(0, bestLoc, loc,
+			pattern), scoreThreshold)
+		// What about in the other direction? (speedup)
+		bestLoc = lastIndexOf(text, pattern, loc+len(pattern))
+		if bestLoc != -1 {
+			scoreThreshold = math.Min(dmp.matchBitapScore(0, bestLoc, loc,
+				pattern), scoreThreshold)
+		}
+	}
+
+	// Initialise the bit arrays.
+	matchmask := 1 << uint((len(pattern) - 1))
+	bestLoc = -1
+
+	var binMin, binMid int
+	binMax := len(pattern) + len(text)
+	lastRd := []int{}
+	for d := 0; d < len(pattern); d++ {
+		// Scan for the best match; each iteration allows for one more error. Run a binary search to determine how far from 'loc' we can stray at this error level.
+		binMin = 0
+		binMid = binMax
+		for binMin < binMid {
+			if dmp.matchBitapScore(d, loc+binMid, loc, pattern) <= scoreThreshold {
+				binMin = binMid
+			} else {
+				binMax = binMid
+			}
+			binMid = (binMax-binMin)/2 + binMin
+		}
+		// Use the result from this iteration as the maximum for the next.
+		binMax = binMid
+		start := int(math.Max(1, float64(loc-binMid+1)))
+		finish := int(math.Min(float64(loc+binMid), float64(len(text))) + float64(len(pattern)))
+
+		rd := make([]int, finish+2)
+		rd[finish+1] = (1 << uint(d)) - 1
+
+		for j := finish; j >= start; j-- {
+			var charMatch int
+			if len(text) <= j-1 {
+				// Out of range.
+				charMatch = 0
+			} else if _, ok := s[text[j-1]]; !ok {
+				charMatch = 0
+			} else {
+				charMatch = s[text[j-1]]
+			}
+
+			if d == 0 {
+				// First pass: exact match.
+				rd[j] = ((rd[j+1] << 1) | 1) & charMatch
+			} else {
+				// Subsequent passes: fuzzy match.
+				rd[j] = ((rd[j+1]<<1)|1)&charMatch | (((lastRd[j+1] | lastRd[j]) << 1) | 1) | lastRd[j+1]
+			}
+			if (rd[j] & matchmask) != 0 {
+				score := dmp.matchBitapScore(d, j-1, loc, pattern)
+				// This match will almost certainly be better than any existing match.  But check anyway.
+				if score <= scoreThreshold {
+					// Told you so.
+					scoreThreshold = score
+					bestLoc = j - 1
+					if bestLoc > loc {
+						// When passing loc, don't exceed our current distance from loc.
+						start = int(math.Max(1, float64(2*loc-bestLoc)))
+					} else {
+						// Already passed loc, downhill from here on in.
+						break
+					}
+				}
+			}
+		}
+		if dmp.matchBitapScore(d+1, loc, loc, pattern) > scoreThreshold {
+			// No hope for a (better) match at greater error levels.
+			break
+		}
+		lastRd = rd
+	}
+	return bestLoc
+}
+
+// matchBitapScore computes and returns the score for a match with e errors and x location.
+func (dmp *DiffMatchPatch) matchBitapScore(e, x, loc int, pattern string) float64 {
+	accuracy := float64(e) / float64(len(pattern))
+	proximity := math.Abs(float64(loc - x))
+	if dmp.MatchDistance == 0 {
+		// Dodge divide by zero error.
+		if proximity == 0 {
+			return accuracy
+		}
+
+		return 1.0
+	}
+	return accuracy + (proximity / float64(dmp.MatchDistance))
+}
+
+// MatchAlphabet initialises the alphabet for the Bitap algorithm.
+func (dmp *DiffMatchPatch) MatchAlphabet(pattern string) map[byte]int {
+	s := map[byte]int{}
+	charPattern := []byte(pattern)
+	for _, c := range charPattern {
+		_, ok := s[c]
+		if !ok {
+			s[c] = 0
+		}
+	}
+	i := 0
+
+	for _, c := range charPattern {
+		value := s[c] | int(uint(1)<<uint((len(pattern)-i-1)))
+		s[c] = value
+		i++
+	}
+	return s
+}
diff --git a/vendor/github.com/sergi/go-diff/diffmatchpatch/mathutil.go b/vendor/github.com/sergi/go-diff/diffmatchpatch/mathutil.go
new file mode 100644
index 00000000..aed242bc
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/diffmatchpatch/mathutil.go
@@ -0,0 +1,23 @@
+// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
+// https://github.com/sergi/go-diff
+// See the included LICENSE file for license details.
+//
+// go-diff is a Go implementation of Google's Diff, Match, and Patch library
+// Original library is Copyright (c) 2006 Google Inc.
+// http://code.google.com/p/google-diff-match-patch/
+
+package diffmatchpatch
+
+func min(x, y int) int {
+	if x < y {
+		return x
+	}
+	return y
+}
+
+func max(x, y int) int {
+	if x > y {
+		return x
+	}
+	return y
+}
diff --git a/vendor/github.com/sergi/go-diff/diffmatchpatch/patch.go b/vendor/github.com/sergi/go-diff/diffmatchpatch/patch.go
new file mode 100644
index 00000000..223c43c4
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/diffmatchpatch/patch.go
@@ -0,0 +1,556 @@
+// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
+// https://github.com/sergi/go-diff
+// See the included LICENSE file for license details.
+//
+// go-diff is a Go implementation of Google's Diff, Match, and Patch library
+// Original library is Copyright (c) 2006 Google Inc.
+// http://code.google.com/p/google-diff-match-patch/
+
+package diffmatchpatch
+
+import (
+	"bytes"
+	"errors"
+	"math"
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// Patch represents one patch operation.
+type Patch struct {
+	diffs   []Diff
+	Start1  int
+	Start2  int
+	Length1 int
+	Length2 int
+}
+
+// String emulates GNU diff's format.
+// Header: @@ -382,8 +481,9 @@
+// Indices are printed as 1-based, not 0-based.
+func (p *Patch) String() string {
+	var coords1, coords2 string
+
+	if p.Length1 == 0 {
+		coords1 = strconv.Itoa(p.Start1) + ",0"
+	} else if p.Length1 == 1 {
+		coords1 = strconv.Itoa(p.Start1 + 1)
+	} else {
+		coords1 = strconv.Itoa(p.Start1+1) + "," + strconv.Itoa(p.Length1)
+	}
+
+	if p.Length2 == 0 {
+		coords2 = strconv.Itoa(p.Start2) + ",0"
+	} else if p.Length2 == 1 {
+		coords2 = strconv.Itoa(p.Start2 + 1)
+	} else {
+		coords2 = strconv.Itoa(p.Start2+1) + "," + strconv.Itoa(p.Length2)
+	}
+
+	var text bytes.Buffer
+	_, _ = text.WriteString("@@ -" + coords1 + " +" + coords2 + " @@\n")
+
+	// Escape the body of the patch with %xx notation.
+	for _, aDiff := range p.diffs {
+		switch aDiff.Type {
+		case DiffInsert:
+			_, _ = text.WriteString("+")
+		case DiffDelete:
+			_, _ = text.WriteString("-")
+		case DiffEqual:
+			_, _ = text.WriteString(" ")
+		}
+
+		_, _ = text.WriteString(strings.Replace(url.QueryEscape(aDiff.Text), "+", " ", -1))
+		_, _ = text.WriteString("\n")
+	}
+
+	return unescaper.Replace(text.String())
+}
+
+// PatchAddContext increases the context until it is unique, but doesn't let the pattern expand beyond MatchMaxBits.
+func (dmp *DiffMatchPatch) PatchAddContext(patch Patch, text string) Patch {
+	if len(text) == 0 {
+		return patch
+	}
+
+	pattern := text[patch.Start2 : patch.Start2+patch.Length1]
+	padding := 0
+
+	// Look for the first and last matches of pattern in text.  If two different matches are found, increase the pattern length.
+	for strings.Index(text, pattern) != strings.LastIndex(text, pattern) &&
+		len(pattern) < dmp.MatchMaxBits-2*dmp.PatchMargin {
+		padding += dmp.PatchMargin
+		maxStart := max(0, patch.Start2-padding)
+		minEnd := min(len(text), patch.Start2+patch.Length1+padding)
+		pattern = text[maxStart:minEnd]
+	}
+	// Add one chunk for good luck.
+	padding += dmp.PatchMargin
+
+	// Add the prefix.
+	prefix := text[max(0, patch.Start2-padding):patch.Start2]
+	if len(prefix) != 0 {
+		patch.diffs = append([]Diff{Diff{DiffEqual, prefix}}, patch.diffs...)
+	}
+	// Add the suffix.
+	suffix := text[patch.Start2+patch.Length1 : min(len(text), patch.Start2+patch.Length1+padding)]
+	if len(suffix) != 0 {
+		patch.diffs = append(patch.diffs, Diff{DiffEqual, suffix})
+	}
+
+	// Roll back the start points.
+	patch.Start1 -= len(prefix)
+	patch.Start2 -= len(prefix)
+	// Extend the lengths.
+	patch.Length1 += len(prefix) + len(suffix)
+	patch.Length2 += len(prefix) + len(suffix)
+
+	return patch
+}
+
+// PatchMake computes a list of patches.
+func (dmp *DiffMatchPatch) PatchMake(opt ...interface{}) []Patch {
+	if len(opt) == 1 {
+		diffs, _ := opt[0].([]Diff)
+		text1 := dmp.DiffText1(diffs)
+		return dmp.PatchMake(text1, diffs)
+	} else if len(opt) == 2 {
+		text1 := opt[0].(string)
+		switch t := opt[1].(type) {
+		case string:
+			diffs := dmp.DiffMain(text1, t, true)
+			if len(diffs) > 2 {
+				diffs = dmp.DiffCleanupSemantic(diffs)
+				diffs = dmp.DiffCleanupEfficiency(diffs)
+			}
+			return dmp.PatchMake(text1, diffs)
+		case []Diff:
+			return dmp.patchMake2(text1, t)
+		}
+	} else if len(opt) == 3 {
+		return dmp.PatchMake(opt[0], opt[2])
+	}
+	return []Patch{}
+}
+
+// patchMake2 computes a list of patches to turn text1 into text2.
+// text2 is not provided, diffs are the delta between text1 and text2.
+func (dmp *DiffMatchPatch) patchMake2(text1 string, diffs []Diff) []Patch {
+	// Check for null inputs not needed since null can't be passed in C#.
+	patches := []Patch{}
+	if len(diffs) == 0 {
+		return patches // Get rid of the null case.
+	}
+
+	patch := Patch{}
+	charCount1 := 0 // Number of characters into the text1 string.
+	charCount2 := 0 // Number of characters into the text2 string.
+	// Start with text1 (prepatchText) and apply the diffs until we arrive at text2 (postpatchText). We recreate the patches one by one to determine context info.
+	prepatchText := text1
+	postpatchText := text1
+
+	for i, aDiff := range diffs {
+		if len(patch.diffs) == 0 && aDiff.Type != DiffEqual {
+			// A new patch starts here.
+			patch.Start1 = charCount1
+			patch.Start2 = charCount2
+		}
+
+		switch aDiff.Type {
+		case DiffInsert:
+			patch.diffs = append(patch.diffs, aDiff)
+			patch.Length2 += len(aDiff.Text)
+			postpatchText = postpatchText[:charCount2] +
+				aDiff.Text + postpatchText[charCount2:]
+		case DiffDelete:
+			patch.Length1 += len(aDiff.Text)
+			patch.diffs = append(patch.diffs, aDiff)
+			postpatchText = postpatchText[:charCount2] + postpatchText[charCount2+len(aDiff.Text):]
+		case DiffEqual:
+			if len(aDiff.Text) <= 2*dmp.PatchMargin &&
+				len(patch.diffs) != 0 && i != len(diffs)-1 {
+				// Small equality inside a patch.
+				patch.diffs = append(patch.diffs, aDiff)
+				patch.Length1 += len(aDiff.Text)
+				patch.Length2 += len(aDiff.Text)
+			}
+			if len(aDiff.Text) >= 2*dmp.PatchMargin {
+				// Time for a new patch.
+				if len(patch.diffs) != 0 {
+					patch = dmp.PatchAddContext(patch, prepatchText)
+					patches = append(patches, patch)
+					patch = Patch{}
+					// Unlike Unidiff, our patch lists have a rolling context. http://code.google.com/p/google-diff-match-patch/wiki/Unidiff Update prepatch text & pos to reflect the application of the just completed patch.
+					prepatchText = postpatchText
+					charCount1 = charCount2
+				}
+			}
+		}
+
+		// Update the current character count.
+		if aDiff.Type != DiffInsert {
+			charCount1 += len(aDiff.Text)
+		}
+		if aDiff.Type != DiffDelete {
+			charCount2 += len(aDiff.Text)
+		}
+	}
+
+	// Pick up the leftover patch if not empty.
+	if len(patch.diffs) != 0 {
+		patch = dmp.PatchAddContext(patch, prepatchText)
+		patches = append(patches, patch)
+	}
+
+	return patches
+}
+
+// PatchDeepCopy returns an array that is identical to a given an array of patches.
+func (dmp *DiffMatchPatch) PatchDeepCopy(patches []Patch) []Patch {
+	patchesCopy := []Patch{}
+	for _, aPatch := range patches {
+		patchCopy := Patch{}
+		for _, aDiff := range aPatch.diffs {
+			patchCopy.diffs = append(patchCopy.diffs, Diff{
+				aDiff.Type,
+				aDiff.Text,
+			})
+		}
+		patchCopy.Start1 = aPatch.Start1
+		patchCopy.Start2 = aPatch.Start2
+		patchCopy.Length1 = aPatch.Length1
+		patchCopy.Length2 = aPatch.Length2
+		patchesCopy = append(patchesCopy, patchCopy)
+	}
+	return patchesCopy
+}
+
+// PatchApply merges a set of patches onto the text.  Returns a patched text, as well as an array of true/false values indicating which patches were applied.
+func (dmp *DiffMatchPatch) PatchApply(patches []Patch, text string) (string, []bool) {
+	if len(patches) == 0 {
+		return text, []bool{}
+	}
+
+	// Deep copy the patches so that no changes are made to originals.
+	patches = dmp.PatchDeepCopy(patches)
+
+	nullPadding := dmp.PatchAddPadding(patches)
+	text = nullPadding + text + nullPadding
+	patches = dmp.PatchSplitMax(patches)
+
+	x := 0
+	// delta keeps track of the offset between the expected and actual location of the previous patch.  If there are patches expected at positions 10 and 20, but the first patch was found at 12, delta is 2 and the second patch has an effective expected position of 22.
+	delta := 0
+	results := make([]bool, len(patches))
+	for _, aPatch := range patches {
+		expectedLoc := aPatch.Start2 + delta
+		text1 := dmp.DiffText1(aPatch.diffs)
+		var startLoc int
+		endLoc := -1
+		if len(text1) > dmp.MatchMaxBits {
+			// PatchSplitMax will only provide an oversized pattern in the case of a monster delete.
+			startLoc = dmp.MatchMain(text, text1[:dmp.MatchMaxBits], expectedLoc)
+			if startLoc != -1 {
+				endLoc = dmp.MatchMain(text,
+					text1[len(text1)-dmp.MatchMaxBits:], expectedLoc+len(text1)-dmp.MatchMaxBits)
+				if endLoc == -1 || startLoc >= endLoc {
+					// Can't find valid trailing context.  Drop this patch.
+					startLoc = -1
+				}
+			}
+		} else {
+			startLoc = dmp.MatchMain(text, text1, expectedLoc)
+		}
+		if startLoc == -1 {
+			// No match found.  :(
+			results[x] = false
+			// Subtract the delta for this failed patch from subsequent patches.
+			delta -= aPatch.Length2 - aPatch.Length1
+		} else {
+			// Found a match.  :)
+			results[x] = true
+			delta = startLoc - expectedLoc
+			var text2 string
+			if endLoc == -1 {
+				text2 = text[startLoc:int(math.Min(float64(startLoc+len(text1)), float64(len(text))))]
+			} else {
+				text2 = text[startLoc:int(math.Min(float64(endLoc+dmp.MatchMaxBits), float64(len(text))))]
+			}
+			if text1 == text2 {
+				// Perfect match, just shove the Replacement text in.
+				text = text[:startLoc] + dmp.DiffText2(aPatch.diffs) + text[startLoc+len(text1):]
+			} else {
+				// Imperfect match.  Run a diff to get a framework of equivalent indices.
+				diffs := dmp.DiffMain(text1, text2, false)
+				if len(text1) > dmp.MatchMaxBits && float64(dmp.DiffLevenshtein(diffs))/float64(len(text1)) > dmp.PatchDeleteThreshold {
+					// The end points match, but the content is unacceptably bad.
+					results[x] = false
+				} else {
+					diffs = dmp.DiffCleanupSemanticLossless(diffs)
+					index1 := 0
+					for _, aDiff := range aPatch.diffs {
+						if aDiff.Type != DiffEqual {
+							index2 := dmp.DiffXIndex(diffs, index1)
+							if aDiff.Type == DiffInsert {
+								// Insertion
+								text = text[:startLoc+index2] + aDiff.Text + text[startLoc+index2:]
+							} else if aDiff.Type == DiffDelete {
+								// Deletion
+								startIndex := startLoc + index2
+								text = text[:startIndex] +
+									text[startIndex+dmp.DiffXIndex(diffs, index1+len(aDiff.Text))-index2:]
+							}
+						}
+						if aDiff.Type != DiffDelete {
+							index1 += len(aDiff.Text)
+						}
+					}
+				}
+			}
+		}
+		x++
+	}
+	// Strip the padding off.
+	text = text[len(nullPadding) : len(nullPadding)+(len(text)-2*len(nullPadding))]
+	return text, results
+}
+
+// PatchAddPadding adds some padding on text start and end so that edges can match something.
+// Intended to be called only from within patchApply.
+func (dmp *DiffMatchPatch) PatchAddPadding(patches []Patch) string {
+	paddingLength := dmp.PatchMargin
+	nullPadding := ""
+	for x := 1; x <= paddingLength; x++ {
+		nullPadding += string(x)
+	}
+
+	// Bump all the patches forward.
+	for i := range patches {
+		patches[i].Start1 += paddingLength
+		patches[i].Start2 += paddingLength
+	}
+
+	// Add some padding on start of first diff.
+	if len(patches[0].diffs) == 0 || patches[0].diffs[0].Type != DiffEqual {
+		// Add nullPadding equality.
+		patches[0].diffs = append([]Diff{Diff{DiffEqual, nullPadding}}, patches[0].diffs...)
+		patches[0].Start1 -= paddingLength // Should be 0.
+		patches[0].Start2 -= paddingLength // Should be 0.
+		patches[0].Length1 += paddingLength
+		patches[0].Length2 += paddingLength
+	} else if paddingLength > len(patches[0].diffs[0].Text) {
+		// Grow first equality.
+		extraLength := paddingLength - len(patches[0].diffs[0].Text)
+		patches[0].diffs[0].Text = nullPadding[len(patches[0].diffs[0].Text):] + patches[0].diffs[0].Text
+		patches[0].Start1 -= extraLength
+		patches[0].Start2 -= extraLength
+		patches[0].Length1 += extraLength
+		patches[0].Length2 += extraLength
+	}
+
+	// Add some padding on end of last diff.
+	last := len(patches) - 1
+	if len(patches[last].diffs) == 0 || patches[last].diffs[len(patches[last].diffs)-1].Type != DiffEqual {
+		// Add nullPadding equality.
+		patches[last].diffs = append(patches[last].diffs, Diff{DiffEqual, nullPadding})
+		patches[last].Length1 += paddingLength
+		patches[last].Length2 += paddingLength
+	} else if paddingLength > len(patches[last].diffs[len(patches[last].diffs)-1].Text) {
+		// Grow last equality.
+		lastDiff := patches[last].diffs[len(patches[last].diffs)-1]
+		extraLength := paddingLength - len(lastDiff.Text)
+		patches[last].diffs[len(patches[last].diffs)-1].Text += nullPadding[:extraLength]
+		patches[last].Length1 += extraLength
+		patches[last].Length2 += extraLength
+	}
+
+	return nullPadding
+}
+
+// PatchSplitMax looks through the patches and breaks up any which are longer than the maximum limit of the match algorithm.
+// Intended to be called only from within patchApply.
+func (dmp *DiffMatchPatch) PatchSplitMax(patches []Patch) []Patch {
+	patchSize := dmp.MatchMaxBits
+	for x := 0; x < len(patches); x++ {
+		if patches[x].Length1 <= patchSize {
+			continue
+		}
+		bigpatch := patches[x]
+		// Remove the big old patch.
+		patches = append(patches[:x], patches[x+1:]...)
+		x--
+
+		Start1 := bigpatch.Start1
+		Start2 := bigpatch.Start2
+		precontext := ""
+		for len(bigpatch.diffs) != 0 {
+			// Create one of several smaller patches.
+			patch := Patch{}
+			empty := true
+			patch.Start1 = Start1 - len(precontext)
+			patch.Start2 = Start2 - len(precontext)
+			if len(precontext) != 0 {
+				patch.Length1 = len(precontext)
+				patch.Length2 = len(precontext)
+				patch.diffs = append(patch.diffs, Diff{DiffEqual, precontext})
+			}
+			for len(bigpatch.diffs) != 0 && patch.Length1 < patchSize-dmp.PatchMargin {
+				diffType := bigpatch.diffs[0].Type
+				diffText := bigpatch.diffs[0].Text
+				if diffType == DiffInsert {
+					// Insertions are harmless.
+					patch.Length2 += len(diffText)
+					Start2 += len(diffText)
+					patch.diffs = append(patch.diffs, bigpatch.diffs[0])
+					bigpatch.diffs = bigpatch.diffs[1:]
+					empty = false
+				} else if diffType == DiffDelete && len(patch.diffs) == 1 && patch.diffs[0].Type == DiffEqual && len(diffText) > 2*patchSize {
+					// This is a large deletion.  Let it pass in one chunk.
+					patch.Length1 += len(diffText)
+					Start1 += len(diffText)
+					empty = false
+					patch.diffs = append(patch.diffs, Diff{diffType, diffText})
+					bigpatch.diffs = bigpatch.diffs[1:]
+				} else {
+					// Deletion or equality.  Only take as much as we can stomach.
+					diffText = diffText[:min(len(diffText), patchSize-patch.Length1-dmp.PatchMargin)]
+
+					patch.Length1 += len(diffText)
+					Start1 += len(diffText)
+					if diffType == DiffEqual {
+						patch.Length2 += len(diffText)
+						Start2 += len(diffText)
+					} else {
+						empty = false
+					}
+					patch.diffs = append(patch.diffs, Diff{diffType, diffText})
+					if diffText == bigpatch.diffs[0].Text {
+						bigpatch.diffs = bigpatch.diffs[1:]
+					} else {
+						bigpatch.diffs[0].Text =
+							bigpatch.diffs[0].Text[len(diffText):]
+					}
+				}
+			}
+			// Compute the head context for the next patch.
+			precontext = dmp.DiffText2(patch.diffs)
+			precontext = precontext[max(0, len(precontext)-dmp.PatchMargin):]
+
+			postcontext := ""
+			// Append the end context for this patch.
+			if len(dmp.DiffText1(bigpatch.diffs)) > dmp.PatchMargin {
+				postcontext = dmp.DiffText1(bigpatch.diffs)[:dmp.PatchMargin]
+			} else {
+				postcontext = dmp.DiffText1(bigpatch.diffs)
+			}
+
+			if len(postcontext) != 0 {
+				patch.Length1 += len(postcontext)
+				patch.Length2 += len(postcontext)
+				if len(patch.diffs) != 0 && patch.diffs[len(patch.diffs)-1].Type == DiffEqual {
+					patch.diffs[len(patch.diffs)-1].Text += postcontext
+				} else {
+					patch.diffs = append(patch.diffs, Diff{DiffEqual, postcontext})
+				}
+			}
+			if !empty {
+				x++
+				patches = append(patches[:x], append([]Patch{patch}, patches[x:]...)...)
+			}
+		}
+	}
+	return patches
+}
+
+// PatchToText takes a list of patches and returns a textual representation.
+func (dmp *DiffMatchPatch) PatchToText(patches []Patch) string {
+	var text bytes.Buffer
+	for _, aPatch := range patches {
+		_, _ = text.WriteString(aPatch.String())
+	}
+	return text.String()
+}
+
+// PatchFromText parses a textual representation of patches and returns a List of Patch objects.
+func (dmp *DiffMatchPatch) PatchFromText(textline string) ([]Patch, error) {
+	patches := []Patch{}
+	if len(textline) == 0 {
+		return patches, nil
+	}
+	text := strings.Split(textline, "\n")
+	textPointer := 0
+	patchHeader := regexp.MustCompile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$")
+
+	var patch Patch
+	var sign uint8
+	var line string
+	for textPointer < len(text) {
+
+		if !patchHeader.MatchString(text[textPointer]) {
+			return patches, errors.New("Invalid patch string: " + text[textPointer])
+		}
+
+		patch = Patch{}
+		m := patchHeader.FindStringSubmatch(text[textPointer])
+
+		patch.Start1, _ = strconv.Atoi(m[1])
+		if len(m[2]) == 0 {
+			patch.Start1--
+			patch.Length1 = 1
+		} else if m[2] == "0" {
+			patch.Length1 = 0
+		} else {
+			patch.Start1--
+			patch.Length1, _ = strconv.Atoi(m[2])
+		}
+
+		patch.Start2, _ = strconv.Atoi(m[3])
+
+		if len(m[4]) == 0 {
+			patch.Start2--
+			patch.Length2 = 1
+		} else if m[4] == "0" {
+			patch.Length2 = 0
+		} else {
+			patch.Start2--
+			patch.Length2, _ = strconv.Atoi(m[4])
+		}
+		textPointer++
+
+		for textPointer < len(text) {
+			if len(text[textPointer]) > 0 {
+				sign = text[textPointer][0]
+			} else {
+				textPointer++
+				continue
+			}
+
+			line = text[textPointer][1:]
+			line = strings.Replace(line, "+", "%2b", -1)
+			line, _ = url.QueryUnescape(line)
+			if sign == '-' {
+				// Deletion.
+				patch.diffs = append(patch.diffs, Diff{DiffDelete, line})
+			} else if sign == '+' {
+				// Insertion.
+				patch.diffs = append(patch.diffs, Diff{DiffInsert, line})
+			} else if sign == ' ' {
+				// Minor equality.
+				patch.diffs = append(patch.diffs, Diff{DiffEqual, line})
+			} else if sign == '@' {
+				// Start of next patch.
+				break
+			} else {
+				// WTF?
+				return patches, errors.New("Invalid patch mode '" + string(sign) + "' in: " + string(line))
+			}
+			textPointer++
+		}
+
+		patches = append(patches, patch)
+	}
+	return patches, nil
+}
diff --git a/vendor/github.com/sergi/go-diff/diffmatchpatch/stringutil.go b/vendor/github.com/sergi/go-diff/diffmatchpatch/stringutil.go
new file mode 100644
index 00000000..265f29cc
--- /dev/null
+++ b/vendor/github.com/sergi/go-diff/diffmatchpatch/stringutil.go
@@ -0,0 +1,88 @@
+// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
+// https://github.com/sergi/go-diff
+// See the included LICENSE file for license details.
+//
+// go-diff is a Go implementation of Google's Diff, Match, and Patch library
+// Original library is Copyright (c) 2006 Google Inc.
+// http://code.google.com/p/google-diff-match-patch/
+
+package diffmatchpatch
+
+import (
+	"strings"
+	"unicode/utf8"
+)
+
+// unescaper unescapes selected chars for compatibility with JavaScript's encodeURI.
+// In speed critical applications this could be dropped since the receiving application will certainly decode these fine. Note that this function is case-sensitive.  Thus "%3F" would not be unescaped.  But this is ok because it is only called with the output of HttpUtility.UrlEncode which returns lowercase hex. Example: "%3f" -> "?", "%24" -> "$", etc.
+var unescaper = strings.NewReplacer(
+	"%21", "!", "%7E", "~", "%27", "'",
+	"%28", "(", "%29", ")", "%3B", ";",
+	"%2F", "/", "%3F", "?", "%3A", ":",
+	"%40", "@", "%26", "&", "%3D", "=",
+	"%2B", "+", "%24", "$", "%2C", ",", "%23", "#", "%2A", "*")
+
+// indexOf returns the first index of pattern in str, starting at str[i].
+func indexOf(str string, pattern string, i int) int {
+	if i > len(str)-1 {
+		return -1
+	}
+	if i <= 0 {
+		return strings.Index(str, pattern)
+	}
+	ind := strings.Index(str[i:], pattern)
+	if ind == -1 {
+		return -1
+	}
+	return ind + i
+}
+
+// lastIndexOf returns the last index of pattern in str, starting at str[i].
+func lastIndexOf(str string, pattern string, i int) int {
+	if i < 0 {
+		return -1
+	}
+	if i >= len(str) {
+		return strings.LastIndex(str, pattern)
+	}
+	_, size := utf8.DecodeRuneInString(str[i:])
+	return strings.LastIndex(str[:i+size], pattern)
+}
+
+// runesIndexOf returns the index of pattern in target, starting at target[i].
+func runesIndexOf(target, pattern []rune, i int) int {
+	if i > len(target)-1 {
+		return -1
+	}
+	if i <= 0 {
+		return runesIndex(target, pattern)
+	}
+	ind := runesIndex(target[i:], pattern)
+	if ind == -1 {
+		return -1
+	}
+	return ind + i
+}
+
+func runesEqual(r1, r2 []rune) bool {
+	if len(r1) != len(r2) {
+		return false
+	}
+	for i, c := range r1 {
+		if c != r2[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// runesIndex is the equivalent of strings.Index for rune slices.
+func runesIndex(r1, r2 []rune) int {
+	last := len(r1) - len(r2)
+	for i := 0; i <= last; i++ {
+		if runesEqual(r1[i:i+len(r2)], r2) {
+			return i
+		}
+	}
+	return -1
+}
diff --git a/vendor/github.com/src-d/gcfg/LICENSE b/vendor/github.com/src-d/gcfg/LICENSE
new file mode 100644
index 00000000..87a5cede
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/LICENSE
@@ -0,0 +1,28 @@
+Copyright (c) 2012 Péter Surányi. Portions Copyright (c) 2009 The Go
+Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/vendor/github.com/src-d/gcfg/README b/vendor/github.com/src-d/gcfg/README
new file mode 100644
index 00000000..1ff233a5
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/README
@@ -0,0 +1,4 @@
+Gcfg reads INI-style configuration files into Go structs;
+supports user-defined types and subsections.
+
+Package docs: https://godoc.org/gopkg.in/gcfg.v1
diff --git a/vendor/github.com/src-d/gcfg/doc.go b/vendor/github.com/src-d/gcfg/doc.go
new file mode 100644
index 00000000..2edcb41a
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/doc.go
@@ -0,0 +1,145 @@
+// Package gcfg reads "INI-style" text-based configuration files with
+// "name=value" pairs grouped into sections (gcfg files).
+//
+// This package is still a work in progress; see the sections below for planned
+// changes.
+//
+// Syntax
+//
+// The syntax is based on that used by git config:
+// http://git-scm.com/docs/git-config#_syntax .
+// There are some (planned) differences compared to the git config format:
+//  - improve data portability:
+//    - must be encoded in UTF-8 (for now) and must not contain the 0 byte
+//    - include and "path" type is not supported
+//      (path type may be implementable as a user-defined type)
+//  - internationalization
+//    - section and variable names can contain unicode letters, unicode digits
+//      (as defined in http://golang.org/ref/spec#Characters ) and hyphens
+//      (U+002D), starting with a unicode letter
+//  - disallow potentially ambiguous or misleading definitions:
+//    - `[sec.sub]` format is not allowed (deprecated in gitconfig)
+//    - `[sec ""]` is not allowed
+//      - use `[sec]` for section name "sec" and empty subsection name
+//    - (planned) within a single file, definitions must be contiguous for each:
+//      - section: '[secA]' -> '[secB]' -> '[secA]' is an error
+//      - subsection: '[sec "A"]' -> '[sec "B"]' -> '[sec "A"]' is an error
+//      - multivalued variable: 'multi=a' -> 'other=x' -> 'multi=b' is an error
+//
+// Data structure
+//
+// The functions in this package read values into a user-defined struct.
+// Each section corresponds to a struct field in the config struct, and each
+// variable in a section corresponds to a data field in the section struct.
+// The mapping of each section or variable name to fields is done either based
+// on the "gcfg" struct tag or by matching the name of the section or variable,
+// ignoring case. In the latter case, hyphens '-' in section and variable names
+// correspond to underscores '_' in field names.
+// Fields must be exported; to use a section or variable name starting with a
+// letter that is neither upper- or lower-case, prefix the field name with 'X'.
+// (See https://code.google.com/p/go/issues/detail?id=5763#c4 .)
+//
+// For sections with subsections, the corresponding field in config must be a
+// map, rather than a struct, with string keys and pointer-to-struct values.
+// Values for subsection variables are stored in the map with the subsection
+// name used as the map key.
+// (Note that unlike section and variable names, subsection names are case
+// sensitive.)
+// When using a map, and there is a section with the same section name but
+// without a subsection name, its values are stored with the empty string used
+// as the key.
+// It is possible to provide default values for subsections in the section
+// "default-<sectionname>" (or by setting values in the corresponding struct
+// field "Default_<sectionname>").
+//
+// The functions in this package panic if config is not a pointer to a struct,
+// or when a field is not of a suitable type (either a struct or a map with
+// string keys and pointer-to-struct values).
+//
+// Parsing of values
+//
+// The section structs in the config struct may contain single-valued or
+// multi-valued variables. Variables of unnamed slice type (that is, a type
+// starting with `[]`) are treated as multi-value; all others (including named
+// slice types) are treated as single-valued variables.
+//
+// Single-valued variables are handled based on the type as follows.
+// Unnamed pointer types (that is, types starting with `*`) are dereferenced,
+// and if necessary, a new instance is allocated.
+//
+// For types implementing the encoding.TextUnmarshaler interface, the
+// UnmarshalText method is used to set the value. Implementing this method is
+// the recommended way for parsing user-defined types.
+//
+// For fields of string kind, the value string is assigned to the field, after
+// unquoting and unescaping as needed.
+// For fields of bool kind, the field is set to true if the value is "true",
+// "yes", "on" or "1", and set to false if the value is "false", "no", "off" or
+// "0", ignoring case. In addition, single-valued bool fields can be specified
+// with a "blank" value (variable name without equals sign and value); in such
+// case the value is set to true.
+//
+// Predefined integer types [u]int(|8|16|32|64) and big.Int are parsed as
+// decimal or hexadecimal (if having '0x' prefix). (This is to prevent
+// unintuitively handling zero-padded numbers as octal.) Other types having
+// [u]int* as the underlying type, such as os.FileMode and uintptr allow
+// decimal, hexadecimal, or octal values.
+// Parsing mode for integer types can be overridden using the struct tag option
+// ",int=mode" where mode is a combination of the 'd', 'h', and 'o' characters
+// (each standing for decimal, hexadecimal, and octal, respectively.)
+//
+// All other types are parsed using fmt.Sscanf with the "%v" verb.
+//
+// For multi-valued variables, each individual value is parsed as above and
+// appended to the slice. If the first value is specified as a "blank" value
+// (variable name without equals sign and value), a new slice is allocated;
+// that is any values previously set in the slice will be ignored.
+//
+// The types subpackage for provides helpers for parsing "enum-like" and integer
+// types.
+//
+// Error handling
+//
+// There are 3 types of errors:
+//
+//  - programmer errors / panics:
+//    - invalid configuration structure
+//  - data errors:
+//    - fatal errors:
+//      - invalid configuration syntax
+//    - warnings:
+//      - data that doesn't belong to any part of the config structure
+//
+// Programmer errors trigger panics. These are should be fixed by the programmer
+// before releasing code that uses gcfg.
+//
+// Data errors cause gcfg to return a non-nil error value. This includes the
+// case when there are extra unknown key-value definitions in the configuration
+// data (extra data).
+// However, in some occasions it is desirable to be able to proceed in
+// situations when the only data error is that of extra data.
+// These errors are handled at a different (warning) priority and can be
+// filtered out programmatically. To ignore extra data warnings, wrap the
+// gcfg.Read*Into invocation into a call to gcfg.FatalOnly.
+//
+// TODO
+//
+// The following is a list of changes under consideration:
+//  - documentation
+//    - self-contained syntax documentation
+//    - more practical examples
+//    - move TODOs to issue tracker (eventually)
+//  - syntax
+//    - reconsider valid escape sequences
+//      (gitconfig doesn't support \r in value, \t in subsection name, etc.)
+//  - reading / parsing gcfg files
+//    - define internal representation structure
+//    - support multiple inputs (readers, strings, files)
+//    - support declaring encoding (?)
+//    - support varying fields sets for subsections (?)
+//  - writing gcfg files
+//  - error handling
+//    - make error context accessible programmatically?
+//    - limit input size?
+//
+package gcfg // import "github.com/src-d/gcfg"
diff --git a/vendor/github.com/src-d/gcfg/errors.go b/vendor/github.com/src-d/gcfg/errors.go
new file mode 100644
index 00000000..853c7602
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/errors.go
@@ -0,0 +1,41 @@
+package gcfg
+
+import (
+	"gopkg.in/warnings.v0"
+)
+
+// FatalOnly filters the results of a Read*Into invocation and returns only
+// fatal errors. That is, errors (warnings) indicating data for unknown
+// sections / variables is ignored. Example invocation:
+//
+//  err := gcfg.FatalOnly(gcfg.ReadFileInto(&cfg, configFile))
+//  if err != nil {
+//      ...
+//
+func FatalOnly(err error) error {
+	return warnings.FatalOnly(err)
+}
+
+func isFatal(err error) bool {
+	_, ok := err.(extraData)
+	return !ok
+}
+
+type extraData struct {
+	section    string
+	subsection *string
+	variable   *string
+}
+
+func (e extraData) Error() string {
+	s := "can't store data at section \"" + e.section + "\""
+	if e.subsection != nil {
+		s += ", subsection \"" + *e.subsection + "\""
+	}
+	if e.variable != nil {
+		s += ", variable \"" + *e.variable + "\""
+	}
+	return s
+}
+
+var _ error = extraData{}
diff --git a/vendor/github.com/src-d/gcfg/go1_0.go b/vendor/github.com/src-d/gcfg/go1_0.go
new file mode 100644
index 00000000..66702107
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/go1_0.go
@@ -0,0 +1,7 @@
+// +build !go1.2
+
+package gcfg
+
+type textUnmarshaler interface {
+	UnmarshalText(text []byte) error
+}
diff --git a/vendor/github.com/src-d/gcfg/go1_2.go b/vendor/github.com/src-d/gcfg/go1_2.go
new file mode 100644
index 00000000..6f5843bc
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/go1_2.go
@@ -0,0 +1,9 @@
+// +build go1.2
+
+package gcfg
+
+import (
+	"encoding"
+)
+
+type textUnmarshaler encoding.TextUnmarshaler
diff --git a/vendor/github.com/src-d/gcfg/read.go b/vendor/github.com/src-d/gcfg/read.go
new file mode 100644
index 00000000..fff0448c
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/read.go
@@ -0,0 +1,273 @@
+package gcfg
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/src-d/gcfg/scanner"
+	"github.com/src-d/gcfg/token"
+	"gopkg.in/warnings.v0"
+)
+
+var unescape = map[rune]rune{'\\': '\\', '"': '"', 'n': '\n', 't': '\t', 'b': '\b'}
+
+// no error: invalid literals should be caught by scanner
+func unquote(s string) string {
+	u, q, esc := make([]rune, 0, len(s)), false, false
+	for _, c := range s {
+		if esc {
+			uc, ok := unescape[c]
+			switch {
+			case ok:
+				u = append(u, uc)
+				fallthrough
+			case !q && c == '\n':
+				esc = false
+				continue
+			}
+			panic("invalid escape sequence")
+		}
+		switch c {
+		case '"':
+			q = !q
+		case '\\':
+			esc = true
+		default:
+			u = append(u, c)
+		}
+	}
+	if q {
+		panic("missing end quote")
+	}
+	if esc {
+		panic("invalid escape sequence")
+	}
+	return string(u)
+}
+
+func read(c *warnings.Collector, callback func(string, string, string, string, bool) error,
+	fset *token.FileSet, file *token.File, src []byte) error {
+	//
+	var s scanner.Scanner
+	var errs scanner.ErrorList
+	s.Init(file, src, func(p token.Position, m string) { errs.Add(p, m) }, 0)
+	sect, sectsub := "", ""
+	pos, tok, lit := s.Scan()
+	errfn := func(msg string) error {
+		return fmt.Errorf("%s: %s", fset.Position(pos), msg)
+	}
+	for {
+		if errs.Len() > 0 {
+			if err := c.Collect(errs.Err()); err != nil {
+				return err
+			}
+		}
+		switch tok {
+		case token.EOF:
+			return nil
+		case token.EOL, token.COMMENT:
+			pos, tok, lit = s.Scan()
+		case token.LBRACK:
+			pos, tok, lit = s.Scan()
+			if errs.Len() > 0 {
+				if err := c.Collect(errs.Err()); err != nil {
+					return err
+				}
+			}
+			if tok != token.IDENT {
+				if err := c.Collect(errfn("expected section name")); err != nil {
+					return err
+				}
+			}
+			sect, sectsub = lit, ""
+			pos, tok, lit = s.Scan()
+			if errs.Len() > 0 {
+				if err := c.Collect(errs.Err()); err != nil {
+					return err
+				}
+			}
+			if tok == token.STRING {
+				sectsub = unquote(lit)
+				if sectsub == "" {
+					if err := c.Collect(errfn("empty subsection name")); err != nil {
+						return err
+					}
+				}
+				pos, tok, lit = s.Scan()
+				if errs.Len() > 0 {
+					if err := c.Collect(errs.Err()); err != nil {
+						return err
+					}
+				}
+			}
+			if tok != token.RBRACK {
+				if sectsub == "" {
+					if err := c.Collect(errfn("expected subsection name or right bracket")); err != nil {
+						return err
+					}
+				}
+				if err := c.Collect(errfn("expected right bracket")); err != nil {
+					return err
+				}
+			}
+			pos, tok, lit = s.Scan()
+			if tok != token.EOL && tok != token.EOF && tok != token.COMMENT {
+				if err := c.Collect(errfn("expected EOL, EOF, or comment")); err != nil {
+					return err
+				}
+			}
+			// If a section/subsection header was found, ensure a
+			// container object is created, even if there are no
+			// variables further down.
+			err := c.Collect(callback(sect, sectsub, "", "", true))
+			if err != nil {
+				return err
+			}
+		case token.IDENT:
+			if sect == "" {
+				if err := c.Collect(errfn("expected section header")); err != nil {
+					return err
+				}
+			}
+			n := lit
+			pos, tok, lit = s.Scan()
+			if errs.Len() > 0 {
+				return errs.Err()
+			}
+			blank, v := tok == token.EOF || tok == token.EOL || tok == token.COMMENT, ""
+			if !blank {
+				if tok != token.ASSIGN {
+					if err := c.Collect(errfn("expected '='")); err != nil {
+						return err
+					}
+				}
+				pos, tok, lit = s.Scan()
+				if errs.Len() > 0 {
+					if err := c.Collect(errs.Err()); err != nil {
+						return err
+					}
+				}
+				if tok != token.STRING {
+					if err := c.Collect(errfn("expected value")); err != nil {
+						return err
+					}
+				}
+				v = unquote(lit)
+				pos, tok, lit = s.Scan()
+				if errs.Len() > 0 {
+					if err := c.Collect(errs.Err()); err != nil {
+						return err
+					}
+				}
+				if tok != token.EOL && tok != token.EOF && tok != token.COMMENT {
+					if err := c.Collect(errfn("expected EOL, EOF, or comment")); err != nil {
+						return err
+					}
+				}
+			}
+			err := c.Collect(callback(sect, sectsub, n, v, blank))
+			if err != nil {
+				return err
+			}
+		default:
+			if sect == "" {
+				if err := c.Collect(errfn("expected section header")); err != nil {
+					return err
+				}
+			}
+			if err := c.Collect(errfn("expected section header or variable declaration")); err != nil {
+				return err
+			}
+		}
+	}
+	panic("never reached")
+}
+
+func readInto(config interface{}, fset *token.FileSet, file *token.File,
+	src []byte) error {
+	//
+	c := warnings.NewCollector(isFatal)
+	firstPassCallback := func(s string, ss string, k string, v string, bv bool) error {
+		return set(c, config, s, ss, k, v, bv, false)
+	}
+	err := read(c, firstPassCallback, fset, file, src)
+	if err != nil {
+		return err
+	}
+	secondPassCallback := func(s string, ss string, k string, v string, bv bool) error {
+		return set(c, config, s, ss, k, v, bv, true)
+	}
+	err = read(c, secondPassCallback, fset, file, src)
+	if err != nil {
+		return err
+	}
+	return c.Done()
+}
+
+// ReadWithCallback reads gcfg formatted data from reader and calls
+// callback with each section and option found.
+//
+// Callback is called with section, subsection, option key, option value
+// and blank value flag as arguments.
+//
+// When a section is found, callback is called with nil subsection, option key
+// and option value.
+//
+// When a subsection is found, callback is called with nil option key and
+// option value.
+//
+// If blank value flag is true, it means that the value was not set for an option
+// (as opposed to set to empty string).
+//
+// If callback returns an error, ReadWithCallback terminates with an error too.
+func ReadWithCallback(reader io.Reader, callback func(string, string, string, string, bool) error) error {
+	src, err := ioutil.ReadAll(reader)
+	if err != nil {
+		return err
+	}
+
+	fset := token.NewFileSet()
+	file := fset.AddFile("", fset.Base(), len(src))
+	c := warnings.NewCollector(isFatal)
+
+	return read(c, callback, fset, file, src)
+}
+
+// ReadInto reads gcfg formatted data from reader and sets the values into the
+// corresponding fields in config.
+func ReadInto(config interface{}, reader io.Reader) error {
+	src, err := ioutil.ReadAll(reader)
+	if err != nil {
+		return err
+	}
+	fset := token.NewFileSet()
+	file := fset.AddFile("", fset.Base(), len(src))
+	return readInto(config, fset, file, src)
+}
+
+// ReadStringInto reads gcfg formatted data from str and sets the values into
+// the corresponding fields in config.
+func ReadStringInto(config interface{}, str string) error {
+	r := strings.NewReader(str)
+	return ReadInto(config, r)
+}
+
+// ReadFileInto reads gcfg formatted data from the file filename and sets the
+// values into the corresponding fields in config.
+func ReadFileInto(config interface{}, filename string) error {
+	f, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	src, err := ioutil.ReadAll(f)
+	if err != nil {
+		return err
+	}
+	fset := token.NewFileSet()
+	file := fset.AddFile(filename, fset.Base(), len(src))
+	return readInto(config, fset, file, src)
+}
diff --git a/vendor/github.com/src-d/gcfg/scanner/errors.go b/vendor/github.com/src-d/gcfg/scanner/errors.go
new file mode 100644
index 00000000..f3fcecac
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/scanner/errors.go
@@ -0,0 +1,121 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package scanner
+
+import (
+	"fmt"
+	"io"
+	"sort"
+)
+
+import (
+	"github.com/src-d/gcfg/token"
+)
+
+// In an ErrorList, an error is represented by an *Error.
+// The position Pos, if valid, points to the beginning of
+// the offending token, and the error condition is described
+// by Msg.
+//
+type Error struct {
+	Pos token.Position
+	Msg string
+}
+
+// Error implements the error interface.
+func (e Error) Error() string {
+	if e.Pos.Filename != "" || e.Pos.IsValid() {
+		// don't print "<unknown position>"
+		// TODO(gri) reconsider the semantics of Position.IsValid
+		return e.Pos.String() + ": " + e.Msg
+	}
+	return e.Msg
+}
+
+// ErrorList is a list of *Errors.
+// The zero value for an ErrorList is an empty ErrorList ready to use.
+//
+type ErrorList []*Error
+
+// Add adds an Error with given position and error message to an ErrorList.
+func (p *ErrorList) Add(pos token.Position, msg string) {
+	*p = append(*p, &Error{pos, msg})
+}
+
+// Reset resets an ErrorList to no errors.
+func (p *ErrorList) Reset() { *p = (*p)[0:0] }
+
+// ErrorList implements the sort Interface.
+func (p ErrorList) Len() int      { return len(p) }
+func (p ErrorList) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+
+func (p ErrorList) Less(i, j int) bool {
+	e := &p[i].Pos
+	f := &p[j].Pos
+	if e.Filename < f.Filename {
+		return true
+	}
+	if e.Filename == f.Filename {
+		return e.Offset < f.Offset
+	}
+	return false
+}
+
+// Sort sorts an ErrorList. *Error entries are sorted by position,
+// other errors are sorted by error message, and before any *Error
+// entry.
+//
+func (p ErrorList) Sort() {
+	sort.Sort(p)
+}
+
+// RemoveMultiples sorts an ErrorList and removes all but the first error per line.
+func (p *ErrorList) RemoveMultiples() {
+	sort.Sort(p)
+	var last token.Position // initial last.Line is != any legal error line
+	i := 0
+	for _, e := range *p {
+		if e.Pos.Filename != last.Filename || e.Pos.Line != last.Line {
+			last = e.Pos
+			(*p)[i] = e
+			i++
+		}
+	}
+	(*p) = (*p)[0:i]
+}
+
+// An ErrorList implements the error interface.
+func (p ErrorList) Error() string {
+	switch len(p) {
+	case 0:
+		return "no errors"
+	case 1:
+		return p[0].Error()
+	}
+	return fmt.Sprintf("%s (and %d more errors)", p[0], len(p)-1)
+}
+
+// Err returns an error equivalent to this error list.
+// If the list is empty, Err returns nil.
+func (p ErrorList) Err() error {
+	if len(p) == 0 {
+		return nil
+	}
+	return p
+}
+
+// PrintError is a utility function that prints a list of errors to w,
+// one error per line, if the err parameter is an ErrorList. Otherwise
+// it prints the err string.
+//
+func PrintError(w io.Writer, err error) {
+	if list, ok := err.(ErrorList); ok {
+		for _, e := range list {
+			fmt.Fprintf(w, "%s\n", e)
+		}
+	} else if err != nil {
+		fmt.Fprintf(w, "%s\n", err)
+	}
+}
diff --git a/vendor/github.com/src-d/gcfg/scanner/scanner.go b/vendor/github.com/src-d/gcfg/scanner/scanner.go
new file mode 100644
index 00000000..b1eef06f
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/scanner/scanner.go
@@ -0,0 +1,342 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package scanner implements a scanner for gcfg configuration text.
+// It takes a []byte as source which can then be tokenized
+// through repeated calls to the Scan method.
+//
+// Note that the API for the scanner package may change to accommodate new
+// features or implementation changes in gcfg.
+//
+package scanner
+
+import (
+	"fmt"
+	"path/filepath"
+	"unicode"
+	"unicode/utf8"
+)
+
+import (
+	"github.com/src-d/gcfg/token"
+)
+
+// An ErrorHandler may be provided to Scanner.Init. If a syntax error is
+// encountered and a handler was installed, the handler is called with a
+// position and an error message. The position points to the beginning of
+// the offending token.
+//
+type ErrorHandler func(pos token.Position, msg string)
+
+// A Scanner holds the scanner's internal state while processing
+// a given text.  It can be allocated as part of another data
+// structure but must be initialized via Init before use.
+//
+type Scanner struct {
+	// immutable state
+	file *token.File  // source file handle
+	dir  string       // directory portion of file.Name()
+	src  []byte       // source
+	err  ErrorHandler // error reporting; or nil
+	mode Mode         // scanning mode
+
+	// scanning state
+	ch         rune // current character
+	offset     int  // character offset
+	rdOffset   int  // reading offset (position after current character)
+	lineOffset int  // current line offset
+	nextVal    bool // next token is expected to be a value
+
+	// public state - ok to modify
+	ErrorCount int // number of errors encountered
+}
+
+// Read the next Unicode char into s.ch.
+// s.ch < 0 means end-of-file.
+//
+func (s *Scanner) next() {
+	if s.rdOffset < len(s.src) {
+		s.offset = s.rdOffset
+		if s.ch == '\n' {
+			s.lineOffset = s.offset
+			s.file.AddLine(s.offset)
+		}
+		r, w := rune(s.src[s.rdOffset]), 1
+		switch {
+		case r == 0:
+			s.error(s.offset, "illegal character NUL")
+		case r >= 0x80:
+			// not ASCII
+			r, w = utf8.DecodeRune(s.src[s.rdOffset:])
+			if r == utf8.RuneError && w == 1 {
+				s.error(s.offset, "illegal UTF-8 encoding")
+			}
+		}
+		s.rdOffset += w
+		s.ch = r
+	} else {
+		s.offset = len(s.src)
+		if s.ch == '\n' {
+			s.lineOffset = s.offset
+			s.file.AddLine(s.offset)
+		}
+		s.ch = -1 // eof
+	}
+}
+
+// A mode value is a set of flags (or 0).
+// They control scanner behavior.
+//
+type Mode uint
+
+const (
+	ScanComments Mode = 1 << iota // return comments as COMMENT tokens
+)
+
+// Init prepares the scanner s to tokenize the text src by setting the
+// scanner at the beginning of src. The scanner uses the file set file
+// for position information and it adds line information for each line.
+// It is ok to re-use the same file when re-scanning the same file as
+// line information which is already present is ignored. Init causes a
+// panic if the file size does not match the src size.
+//
+// Calls to Scan will invoke the error handler err if they encounter a
+// syntax error and err is not nil. Also, for each error encountered,
+// the Scanner field ErrorCount is incremented by one. The mode parameter
+// determines how comments are handled.
+//
+// Note that Init may call err if there is an error in the first character
+// of the file.
+//
+func (s *Scanner) Init(file *token.File, src []byte, err ErrorHandler, mode Mode) {
+	// Explicitly initialize all fields since a scanner may be reused.
+	if file.Size() != len(src) {
+		panic(fmt.Sprintf("file size (%d) does not match src len (%d)", file.Size(), len(src)))
+	}
+	s.file = file
+	s.dir, _ = filepath.Split(file.Name())
+	s.src = src
+	s.err = err
+	s.mode = mode
+
+	s.ch = ' '
+	s.offset = 0
+	s.rdOffset = 0
+	s.lineOffset = 0
+	s.ErrorCount = 0
+	s.nextVal = false
+
+	s.next()
+}
+
+func (s *Scanner) error(offs int, msg string) {
+	if s.err != nil {
+		s.err(s.file.Position(s.file.Pos(offs)), msg)
+	}
+	s.ErrorCount++
+}
+
+func (s *Scanner) scanComment() string {
+	// initial [;#] already consumed
+	offs := s.offset - 1 // position of initial [;#]
+
+	for s.ch != '\n' && s.ch >= 0 {
+		s.next()
+	}
+	return string(s.src[offs:s.offset])
+}
+
+func isLetter(ch rune) bool {
+	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch >= 0x80 && unicode.IsLetter(ch)
+}
+
+func isDigit(ch rune) bool {
+	return '0' <= ch && ch <= '9' || ch >= 0x80 && unicode.IsDigit(ch)
+}
+
+func (s *Scanner) scanIdentifier() string {
+	offs := s.offset
+	for isLetter(s.ch) || isDigit(s.ch) || s.ch == '-' {
+		s.next()
+	}
+	return string(s.src[offs:s.offset])
+}
+
+func (s *Scanner) scanEscape(val bool) {
+	offs := s.offset
+	ch := s.ch
+	s.next() // always make progress
+	switch ch {
+	case '\\', '"':
+		// ok
+	case 'n', 't', 'b':
+		if val {
+			break // ok
+		}
+		fallthrough
+	default:
+		s.error(offs, "unknown escape sequence")
+	}
+}
+
+func (s *Scanner) scanString() string {
+	// '"' opening already consumed
+	offs := s.offset - 1
+
+	for s.ch != '"' {
+		ch := s.ch
+		s.next()
+		if ch == '\n' || ch < 0 {
+			s.error(offs, "string not terminated")
+			break
+		}
+		if ch == '\\' {
+			s.scanEscape(false)
+		}
+	}
+
+	s.next()
+
+	return string(s.src[offs:s.offset])
+}
+
+func stripCR(b []byte) []byte {
+	c := make([]byte, len(b))
+	i := 0
+	for _, ch := range b {
+		if ch != '\r' {
+			c[i] = ch
+			i++
+		}
+	}
+	return c[:i]
+}
+
+func (s *Scanner) scanValString() string {
+	offs := s.offset
+
+	hasCR := false
+	end := offs
+	inQuote := false
+loop:
+	for inQuote || s.ch >= 0 && s.ch != '\n' && s.ch != ';' && s.ch != '#' {
+		ch := s.ch
+		s.next()
+		switch {
+		case inQuote && ch == '\\':
+			s.scanEscape(true)
+		case !inQuote && ch == '\\':
+			if s.ch == '\r' {
+				hasCR = true
+				s.next()
+			}
+			if s.ch != '\n' {
+				s.scanEscape(true)
+			} else {
+				s.next()
+			}
+		case ch == '"':
+			inQuote = !inQuote
+		case ch == '\r':
+			hasCR = true
+		case ch < 0 || inQuote && ch == '\n':
+			s.error(offs, "string not terminated")
+			break loop
+		}
+		if inQuote || !isWhiteSpace(ch) {
+			end = s.offset
+		}
+	}
+
+	lit := s.src[offs:end]
+	if hasCR {
+		lit = stripCR(lit)
+	}
+
+	return string(lit)
+}
+
+func isWhiteSpace(ch rune) bool {
+	return ch == ' ' || ch == '\t' || ch == '\r'
+}
+
+func (s *Scanner) skipWhitespace() {
+	for isWhiteSpace(s.ch) {
+		s.next()
+	}
+}
+
+// Scan scans the next token and returns the token position, the token,
+// and its literal string if applicable. The source end is indicated by
+// token.EOF.
+//
+// If the returned token is a literal (token.IDENT, token.STRING) or
+// token.COMMENT, the literal string has the corresponding value.
+//
+// If the returned token is token.ILLEGAL, the literal string is the
+// offending character.
+//
+// In all other cases, Scan returns an empty literal string.
+//
+// For more tolerant parsing, Scan will return a valid token if
+// possible even if a syntax error was encountered. Thus, even
+// if the resulting token sequence contains no illegal tokens,
+// a client may not assume that no error occurred. Instead it
+// must check the scanner's ErrorCount or the number of calls
+// of the error handler, if there was one installed.
+//
+// Scan adds line information to the file added to the file
+// set with Init. Token positions are relative to that file
+// and thus relative to the file set.
+//
+func (s *Scanner) Scan() (pos token.Pos, tok token.Token, lit string) {
+scanAgain:
+	s.skipWhitespace()
+
+	// current token start
+	pos = s.file.Pos(s.offset)
+
+	// determine token value
+	switch ch := s.ch; {
+	case s.nextVal:
+		lit = s.scanValString()
+		tok = token.STRING
+		s.nextVal = false
+	case isLetter(ch):
+		lit = s.scanIdentifier()
+		tok = token.IDENT
+	default:
+		s.next() // always make progress
+		switch ch {
+		case -1:
+			tok = token.EOF
+		case '\n':
+			tok = token.EOL
+		case '"':
+			tok = token.STRING
+			lit = s.scanString()
+		case '[':
+			tok = token.LBRACK
+		case ']':
+			tok = token.RBRACK
+		case ';', '#':
+			// comment
+			lit = s.scanComment()
+			if s.mode&ScanComments == 0 {
+				// skip comment
+				goto scanAgain
+			}
+			tok = token.COMMENT
+		case '=':
+			tok = token.ASSIGN
+			s.nextVal = true
+		default:
+			s.error(s.file.Offset(pos), fmt.Sprintf("illegal character %#U", ch))
+			tok = token.ILLEGAL
+			lit = string(ch)
+		}
+	}
+
+	return
+}
diff --git a/vendor/github.com/src-d/gcfg/set.go b/vendor/github.com/src-d/gcfg/set.go
new file mode 100644
index 00000000..771258f0
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/set.go
@@ -0,0 +1,332 @@
+package gcfg
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+	"math/big"
+	"reflect"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+
+	"github.com/src-d/gcfg/types"
+	"gopkg.in/warnings.v0"
+)
+
+type tag struct {
+	ident   string
+	intMode string
+}
+
+func newTag(ts string) tag {
+	t := tag{}
+	s := strings.Split(ts, ",")
+	t.ident = s[0]
+	for _, tse := range s[1:] {
+		if strings.HasPrefix(tse, "int=") {
+			t.intMode = tse[len("int="):]
+		}
+	}
+	return t
+}
+
+func fieldFold(v reflect.Value, name string) (reflect.Value, tag) {
+	var n string
+	r0, _ := utf8.DecodeRuneInString(name)
+	if unicode.IsLetter(r0) && !unicode.IsLower(r0) && !unicode.IsUpper(r0) {
+		n = "X"
+	}
+	n += strings.Replace(name, "-", "_", -1)
+	f, ok := v.Type().FieldByNameFunc(func(fieldName string) bool {
+		if !v.FieldByName(fieldName).CanSet() {
+			return false
+		}
+		f, _ := v.Type().FieldByName(fieldName)
+		t := newTag(f.Tag.Get("gcfg"))
+		if t.ident != "" {
+			return strings.EqualFold(t.ident, name)
+		}
+		return strings.EqualFold(n, fieldName)
+	})
+	if !ok {
+		return reflect.Value{}, tag{}
+	}
+	return v.FieldByName(f.Name), newTag(f.Tag.Get("gcfg"))
+}
+
+type setter func(destp interface{}, blank bool, val string, t tag) error
+
+var errUnsupportedType = fmt.Errorf("unsupported type")
+var errBlankUnsupported = fmt.Errorf("blank value not supported for type")
+
+var setters = []setter{
+	typeSetter, textUnmarshalerSetter, kindSetter, scanSetter,
+}
+
+func textUnmarshalerSetter(d interface{}, blank bool, val string, t tag) error {
+	dtu, ok := d.(textUnmarshaler)
+	if !ok {
+		return errUnsupportedType
+	}
+	if blank {
+		return errBlankUnsupported
+	}
+	return dtu.UnmarshalText([]byte(val))
+}
+
+func boolSetter(d interface{}, blank bool, val string, t tag) error {
+	if blank {
+		reflect.ValueOf(d).Elem().Set(reflect.ValueOf(true))
+		return nil
+	}
+	b, err := types.ParseBool(val)
+	if err == nil {
+		reflect.ValueOf(d).Elem().Set(reflect.ValueOf(b))
+	}
+	return err
+}
+
+func intMode(mode string) types.IntMode {
+	var m types.IntMode
+	if strings.ContainsAny(mode, "dD") {
+		m |= types.Dec
+	}
+	if strings.ContainsAny(mode, "hH") {
+		m |= types.Hex
+	}
+	if strings.ContainsAny(mode, "oO") {
+		m |= types.Oct
+	}
+	return m
+}
+
+var typeModes = map[reflect.Type]types.IntMode{
+	reflect.TypeOf(int(0)):    types.Dec | types.Hex,
+	reflect.TypeOf(int8(0)):   types.Dec | types.Hex,
+	reflect.TypeOf(int16(0)):  types.Dec | types.Hex,
+	reflect.TypeOf(int32(0)):  types.Dec | types.Hex,
+	reflect.TypeOf(int64(0)):  types.Dec | types.Hex,
+	reflect.TypeOf(uint(0)):   types.Dec | types.Hex,
+	reflect.TypeOf(uint8(0)):  types.Dec | types.Hex,
+	reflect.TypeOf(uint16(0)): types.Dec | types.Hex,
+	reflect.TypeOf(uint32(0)): types.Dec | types.Hex,
+	reflect.TypeOf(uint64(0)): types.Dec | types.Hex,
+	// use default mode (allow dec/hex/oct) for uintptr type
+	reflect.TypeOf(big.Int{}): types.Dec | types.Hex,
+}
+
+func intModeDefault(t reflect.Type) types.IntMode {
+	m, ok := typeModes[t]
+	if !ok {
+		m = types.Dec | types.Hex | types.Oct
+	}
+	return m
+}
+
+func intSetter(d interface{}, blank bool, val string, t tag) error {
+	if blank {
+		return errBlankUnsupported
+	}
+	mode := intMode(t.intMode)
+	if mode == 0 {
+		mode = intModeDefault(reflect.TypeOf(d).Elem())
+	}
+	return types.ParseInt(d, val, mode)
+}
+
+func stringSetter(d interface{}, blank bool, val string, t tag) error {
+	if blank {
+		return errBlankUnsupported
+	}
+	dsp, ok := d.(*string)
+	if !ok {
+		return errUnsupportedType
+	}
+	*dsp = val
+	return nil
+}
+
+var kindSetters = map[reflect.Kind]setter{
+	reflect.String:  stringSetter,
+	reflect.Bool:    boolSetter,
+	reflect.Int:     intSetter,
+	reflect.Int8:    intSetter,
+	reflect.Int16:   intSetter,
+	reflect.Int32:   intSetter,
+	reflect.Int64:   intSetter,
+	reflect.Uint:    intSetter,
+	reflect.Uint8:   intSetter,
+	reflect.Uint16:  intSetter,
+	reflect.Uint32:  intSetter,
+	reflect.Uint64:  intSetter,
+	reflect.Uintptr: intSetter,
+}
+
+var typeSetters = map[reflect.Type]setter{
+	reflect.TypeOf(big.Int{}): intSetter,
+}
+
+func typeSetter(d interface{}, blank bool, val string, tt tag) error {
+	t := reflect.ValueOf(d).Type().Elem()
+	setter, ok := typeSetters[t]
+	if !ok {
+		return errUnsupportedType
+	}
+	return setter(d, blank, val, tt)
+}
+
+func kindSetter(d interface{}, blank bool, val string, tt tag) error {
+	k := reflect.ValueOf(d).Type().Elem().Kind()
+	setter, ok := kindSetters[k]
+	if !ok {
+		return errUnsupportedType
+	}
+	return setter(d, blank, val, tt)
+}
+
+func scanSetter(d interface{}, blank bool, val string, tt tag) error {
+	if blank {
+		return errBlankUnsupported
+	}
+	return types.ScanFully(d, val, 'v')
+}
+
+func newValue(c *warnings.Collector, sect string, vCfg reflect.Value,
+	vType reflect.Type) (reflect.Value, error) {
+	//
+	pv := reflect.New(vType)
+	dfltName := "default-" + sect
+	dfltField, _ := fieldFold(vCfg, dfltName)
+	var err error
+	if dfltField.IsValid() {
+		b := bytes.NewBuffer(nil)
+		ge := gob.NewEncoder(b)
+		if err = c.Collect(ge.EncodeValue(dfltField)); err != nil {
+			return pv, err
+		}
+		gd := gob.NewDecoder(bytes.NewReader(b.Bytes()))
+		if err = c.Collect(gd.DecodeValue(pv.Elem())); err != nil {
+			return pv, err
+		}
+	}
+	return pv, nil
+}
+
+func set(c *warnings.Collector, cfg interface{}, sect, sub, name string,
+	 value string, blankValue bool, subsectPass bool) error {
+	//
+	vPCfg := reflect.ValueOf(cfg)
+	if vPCfg.Kind() != reflect.Ptr || vPCfg.Elem().Kind() != reflect.Struct {
+		panic(fmt.Errorf("config must be a pointer to a struct"))
+	}
+	vCfg := vPCfg.Elem()
+	vSect, _ := fieldFold(vCfg, sect)
+	if !vSect.IsValid() {
+		err := extraData{section: sect}
+		return c.Collect(err)
+	}
+	isSubsect := vSect.Kind() == reflect.Map
+	if subsectPass != isSubsect {
+		return nil
+	}
+	if isSubsect {
+		vst := vSect.Type()
+		if vst.Key().Kind() != reflect.String ||
+			vst.Elem().Kind() != reflect.Ptr ||
+			vst.Elem().Elem().Kind() != reflect.Struct {
+			panic(fmt.Errorf("map field for section must have string keys and "+
+				" pointer-to-struct values: section %q", sect))
+		}
+		if vSect.IsNil() {
+			vSect.Set(reflect.MakeMap(vst))
+		}
+		k := reflect.ValueOf(sub)
+		pv := vSect.MapIndex(k)
+		if !pv.IsValid() {
+			vType := vSect.Type().Elem().Elem()
+			var err error
+			if pv, err = newValue(c, sect, vCfg, vType); err != nil {
+				return err
+			}
+			vSect.SetMapIndex(k, pv)
+		}
+		vSect = pv.Elem()
+	} else if vSect.Kind() != reflect.Struct {
+		panic(fmt.Errorf("field for section must be a map or a struct: "+
+			"section %q", sect))
+	} else if sub != "" {
+		err := extraData{section: sect, subsection: &sub}
+		return c.Collect(err)
+	}
+	// Empty name is a special value, meaning that only the
+	// section/subsection object is to be created, with no values set.
+	if name == "" {
+		return nil
+	}
+	vVar, t := fieldFold(vSect, name)
+	if !vVar.IsValid() {
+		var err error
+		if isSubsect {
+			err = extraData{section: sect, subsection: &sub, variable: &name}
+		} else {
+			err = extraData{section: sect, variable: &name}
+		}
+		return c.Collect(err)
+	}
+	// vVal is either single-valued var, or newly allocated value within multi-valued var
+	var vVal reflect.Value
+	// multi-value if unnamed slice type
+	isMulti := vVar.Type().Name() == "" && vVar.Kind() == reflect.Slice ||
+		vVar.Type().Name() == "" && vVar.Kind() == reflect.Ptr && vVar.Type().Elem().Name() == "" && vVar.Type().Elem().Kind() == reflect.Slice
+	if isMulti && vVar.Kind() == reflect.Ptr {
+		if vVar.IsNil() {
+			vVar.Set(reflect.New(vVar.Type().Elem()))
+		}
+		vVar = vVar.Elem()
+	}
+	if isMulti && blankValue {
+		vVar.Set(reflect.Zero(vVar.Type()))
+		return nil
+	}
+	if isMulti {
+		vVal = reflect.New(vVar.Type().Elem()).Elem()
+	} else {
+		vVal = vVar
+	}
+	isDeref := vVal.Type().Name() == "" && vVal.Type().Kind() == reflect.Ptr
+	isNew := isDeref && vVal.IsNil()
+	// vAddr is address of value to set (dereferenced & allocated as needed)
+	var vAddr reflect.Value
+	switch {
+	case isNew:
+		vAddr = reflect.New(vVal.Type().Elem())
+	case isDeref && !isNew:
+		vAddr = vVal
+	default:
+		vAddr = vVal.Addr()
+	}
+	vAddrI := vAddr.Interface()
+	err, ok := error(nil), false
+	for _, s := range setters {
+		err = s(vAddrI, blankValue, value, t)
+		if err == nil {
+			ok = true
+			break
+		}
+		if err != errUnsupportedType {
+			return err
+		}
+	}
+	if !ok {
+		// in case all setters returned errUnsupportedType
+		return err
+	}
+	if isNew { // set reference if it was dereferenced and newly allocated
+		vVal.Set(vAddr)
+	}
+	if isMulti { // append if multi-valued
+		vVar.Set(reflect.Append(vVar, vVal))
+	}
+	return nil
+}
diff --git a/vendor/github.com/src-d/gcfg/token/position.go b/vendor/github.com/src-d/gcfg/token/position.go
new file mode 100644
index 00000000..fc45c1e7
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/token/position.go
@@ -0,0 +1,435 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TODO(gri) consider making this a separate package outside the go directory.
+
+package token
+
+import (
+	"fmt"
+	"sort"
+	"sync"
+)
+
+// -----------------------------------------------------------------------------
+// Positions
+
+// Position describes an arbitrary source position
+// including the file, line, and column location.
+// A Position is valid if the line number is > 0.
+//
+type Position struct {
+	Filename string // filename, if any
+	Offset   int    // offset, starting at 0
+	Line     int    // line number, starting at 1
+	Column   int    // column number, starting at 1 (character count)
+}
+
+// IsValid returns true if the position is valid.
+func (pos *Position) IsValid() bool { return pos.Line > 0 }
+
+// String returns a string in one of several forms:
+//
+//	file:line:column    valid position with file name
+//	line:column         valid position without file name
+//	file                invalid position with file name
+//	-                   invalid position without file name
+//
+func (pos Position) String() string {
+	s := pos.Filename
+	if pos.IsValid() {
+		if s != "" {
+			s += ":"
+		}
+		s += fmt.Sprintf("%d:%d", pos.Line, pos.Column)
+	}
+	if s == "" {
+		s = "-"
+	}
+	return s
+}
+
+// Pos is a compact encoding of a source position within a file set.
+// It can be converted into a Position for a more convenient, but much
+// larger, representation.
+//
+// The Pos value for a given file is a number in the range [base, base+size],
+// where base and size are specified when adding the file to the file set via
+// AddFile.
+//
+// To create the Pos value for a specific source offset, first add
+// the respective file to the current file set (via FileSet.AddFile)
+// and then call File.Pos(offset) for that file. Given a Pos value p
+// for a specific file set fset, the corresponding Position value is
+// obtained by calling fset.Position(p).
+//
+// Pos values can be compared directly with the usual comparison operators:
+// If two Pos values p and q are in the same file, comparing p and q is
+// equivalent to comparing the respective source file offsets. If p and q
+// are in different files, p < q is true if the file implied by p was added
+// to the respective file set before the file implied by q.
+//
+type Pos int
+
+// The zero value for Pos is NoPos; there is no file and line information
+// associated with it, and NoPos().IsValid() is false. NoPos is always
+// smaller than any other Pos value. The corresponding Position value
+// for NoPos is the zero value for Position.
+//
+const NoPos Pos = 0
+
+// IsValid returns true if the position is valid.
+func (p Pos) IsValid() bool {
+	return p != NoPos
+}
+
+// -----------------------------------------------------------------------------
+// File
+
+// A File is a handle for a file belonging to a FileSet.
+// A File has a name, size, and line offset table.
+//
+type File struct {
+	set  *FileSet
+	name string // file name as provided to AddFile
+	base int    // Pos value range for this file is [base...base+size]
+	size int    // file size as provided to AddFile
+
+	// lines and infos are protected by set.mutex
+	lines []int
+	infos []lineInfo
+}
+
+// Name returns the file name of file f as registered with AddFile.
+func (f *File) Name() string {
+	return f.name
+}
+
+// Base returns the base offset of file f as registered with AddFile.
+func (f *File) Base() int {
+	return f.base
+}
+
+// Size returns the size of file f as registered with AddFile.
+func (f *File) Size() int {
+	return f.size
+}
+
+// LineCount returns the number of lines in file f.
+func (f *File) LineCount() int {
+	f.set.mutex.RLock()
+	n := len(f.lines)
+	f.set.mutex.RUnlock()
+	return n
+}
+
+// AddLine adds the line offset for a new line.
+// The line offset must be larger than the offset for the previous line
+// and smaller than the file size; otherwise the line offset is ignored.
+//
+func (f *File) AddLine(offset int) {
+	f.set.mutex.Lock()
+	if i := len(f.lines); (i == 0 || f.lines[i-1] < offset) && offset < f.size {
+		f.lines = append(f.lines, offset)
+	}
+	f.set.mutex.Unlock()
+}
+
+// SetLines sets the line offsets for a file and returns true if successful.
+// The line offsets are the offsets of the first character of each line;
+// for instance for the content "ab\nc\n" the line offsets are {0, 3}.
+// An empty file has an empty line offset table.
+// Each line offset must be larger than the offset for the previous line
+// and smaller than the file size; otherwise SetLines fails and returns
+// false.
+//
+func (f *File) SetLines(lines []int) bool {
+	// verify validity of lines table
+	size := f.size
+	for i, offset := range lines {
+		if i > 0 && offset <= lines[i-1] || size <= offset {
+			return false
+		}
+	}
+
+	// set lines table
+	f.set.mutex.Lock()
+	f.lines = lines
+	f.set.mutex.Unlock()
+	return true
+}
+
+// SetLinesForContent sets the line offsets for the given file content.
+func (f *File) SetLinesForContent(content []byte) {
+	var lines []int
+	line := 0
+	for offset, b := range content {
+		if line >= 0 {
+			lines = append(lines, line)
+		}
+		line = -1
+		if b == '\n' {
+			line = offset + 1
+		}
+	}
+
+	// set lines table
+	f.set.mutex.Lock()
+	f.lines = lines
+	f.set.mutex.Unlock()
+}
+
+// A lineInfo object describes alternative file and line number
+// information (such as provided via a //line comment in a .go
+// file) for a given file offset.
+type lineInfo struct {
+	// fields are exported to make them accessible to gob
+	Offset   int
+	Filename string
+	Line     int
+}
+
+// AddLineInfo adds alternative file and line number information for
+// a given file offset. The offset must be larger than the offset for
+// the previously added alternative line info and smaller than the
+// file size; otherwise the information is ignored.
+//
+// AddLineInfo is typically used to register alternative position
+// information for //line filename:line comments in source files.
+//
+func (f *File) AddLineInfo(offset int, filename string, line int) {
+	f.set.mutex.Lock()
+	if i := len(f.infos); i == 0 || f.infos[i-1].Offset < offset && offset < f.size {
+		f.infos = append(f.infos, lineInfo{offset, filename, line})
+	}
+	f.set.mutex.Unlock()
+}
+
+// Pos returns the Pos value for the given file offset;
+// the offset must be <= f.Size().
+// f.Pos(f.Offset(p)) == p.
+//
+func (f *File) Pos(offset int) Pos {
+	if offset > f.size {
+		panic("illegal file offset")
+	}
+	return Pos(f.base + offset)
+}
+
+// Offset returns the offset for the given file position p;
+// p must be a valid Pos value in that file.
+// f.Offset(f.Pos(offset)) == offset.
+//
+func (f *File) Offset(p Pos) int {
+	if int(p) < f.base || int(p) > f.base+f.size {
+		panic("illegal Pos value")
+	}
+	return int(p) - f.base
+}
+
+// Line returns the line number for the given file position p;
+// p must be a Pos value in that file or NoPos.
+//
+func (f *File) Line(p Pos) int {
+	// TODO(gri) this can be implemented much more efficiently
+	return f.Position(p).Line
+}
+
+func searchLineInfos(a []lineInfo, x int) int {
+	return sort.Search(len(a), func(i int) bool { return a[i].Offset > x }) - 1
+}
+
+// info returns the file name, line, and column number for a file offset.
+func (f *File) info(offset int) (filename string, line, column int) {
+	filename = f.name
+	if i := searchInts(f.lines, offset); i >= 0 {
+		line, column = i+1, offset-f.lines[i]+1
+	}
+	if len(f.infos) > 0 {
+		// almost no files have extra line infos
+		if i := searchLineInfos(f.infos, offset); i >= 0 {
+			alt := &f.infos[i]
+			filename = alt.Filename
+			if i := searchInts(f.lines, alt.Offset); i >= 0 {
+				line += alt.Line - i - 1
+			}
+		}
+	}
+	return
+}
+
+func (f *File) position(p Pos) (pos Position) {
+	offset := int(p) - f.base
+	pos.Offset = offset
+	pos.Filename, pos.Line, pos.Column = f.info(offset)
+	return
+}
+
+// Position returns the Position value for the given file position p;
+// p must be a Pos value in that file or NoPos.
+//
+func (f *File) Position(p Pos) (pos Position) {
+	if p != NoPos {
+		if int(p) < f.base || int(p) > f.base+f.size {
+			panic("illegal Pos value")
+		}
+		pos = f.position(p)
+	}
+	return
+}
+
+// -----------------------------------------------------------------------------
+// FileSet
+
+// A FileSet represents a set of source files.
+// Methods of file sets are synchronized; multiple goroutines
+// may invoke them concurrently.
+//
+type FileSet struct {
+	mutex sync.RWMutex // protects the file set
+	base  int          // base offset for the next file
+	files []*File      // list of files in the order added to the set
+	last  *File        // cache of last file looked up
+}
+
+// NewFileSet creates a new file set.
+func NewFileSet() *FileSet {
+	s := new(FileSet)
+	s.base = 1 // 0 == NoPos
+	return s
+}
+
+// Base returns the minimum base offset that must be provided to
+// AddFile when adding the next file.
+//
+func (s *FileSet) Base() int {
+	s.mutex.RLock()
+	b := s.base
+	s.mutex.RUnlock()
+	return b
+
+}
+
+// AddFile adds a new file with a given filename, base offset, and file size
+// to the file set s and returns the file. Multiple files may have the same
+// name. The base offset must not be smaller than the FileSet's Base(), and
+// size must not be negative.
+//
+// Adding the file will set the file set's Base() value to base + size + 1
+// as the minimum base value for the next file. The following relationship
+// exists between a Pos value p for a given file offset offs:
+//
+//	int(p) = base + offs
+//
+// with offs in the range [0, size] and thus p in the range [base, base+size].
+// For convenience, File.Pos may be used to create file-specific position
+// values from a file offset.
+//
+func (s *FileSet) AddFile(filename string, base, size int) *File {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	if base < s.base || size < 0 {
+		panic("illegal base or size")
+	}
+	// base >= s.base && size >= 0
+	f := &File{s, filename, base, size, []int{0}, nil}
+	base += size + 1 // +1 because EOF also has a position
+	if base < 0 {
+		panic("token.Pos offset overflow (> 2G of source code in file set)")
+	}
+	// add the file to the file set
+	s.base = base
+	s.files = append(s.files, f)
+	s.last = f
+	return f
+}
+
+// Iterate calls f for the files in the file set in the order they were added
+// until f returns false.
+//
+func (s *FileSet) Iterate(f func(*File) bool) {
+	for i := 0; ; i++ {
+		var file *File
+		s.mutex.RLock()
+		if i < len(s.files) {
+			file = s.files[i]
+		}
+		s.mutex.RUnlock()
+		if file == nil || !f(file) {
+			break
+		}
+	}
+}
+
+func searchFiles(a []*File, x int) int {
+	return sort.Search(len(a), func(i int) bool { return a[i].base > x }) - 1
+}
+
+func (s *FileSet) file(p Pos) *File {
+	// common case: p is in last file
+	if f := s.last; f != nil && f.base <= int(p) && int(p) <= f.base+f.size {
+		return f
+	}
+	// p is not in last file - search all files
+	if i := searchFiles(s.files, int(p)); i >= 0 {
+		f := s.files[i]
+		// f.base <= int(p) by definition of searchFiles
+		if int(p) <= f.base+f.size {
+			s.last = f
+			return f
+		}
+	}
+	return nil
+}
+
+// File returns the file that contains the position p.
+// If no such file is found (for instance for p == NoPos),
+// the result is nil.
+//
+func (s *FileSet) File(p Pos) (f *File) {
+	if p != NoPos {
+		s.mutex.RLock()
+		f = s.file(p)
+		s.mutex.RUnlock()
+	}
+	return
+}
+
+// Position converts a Pos in the fileset into a general Position.
+func (s *FileSet) Position(p Pos) (pos Position) {
+	if p != NoPos {
+		s.mutex.RLock()
+		if f := s.file(p); f != nil {
+			pos = f.position(p)
+		}
+		s.mutex.RUnlock()
+	}
+	return
+}
+
+// -----------------------------------------------------------------------------
+// Helper functions
+
+func searchInts(a []int, x int) int {
+	// This function body is a manually inlined version of:
+	//
+	//   return sort.Search(len(a), func(i int) bool { return a[i] > x }) - 1
+	//
+	// With better compiler optimizations, this may not be needed in the
+	// future, but at the moment this change improves the go/printer
+	// benchmark performance by ~30%. This has a direct impact on the
+	// speed of gofmt and thus seems worthwhile (2011-04-29).
+	// TODO(gri): Remove this when compilers have caught up.
+	i, j := 0, len(a)
+	for i < j {
+		h := i + (j-i)/2 // avoid overflow when computing h
+		// i ≤ h < j
+		if a[h] <= x {
+			i = h + 1
+		} else {
+			j = h
+		}
+	}
+	return i - 1
+}
diff --git a/vendor/github.com/src-d/gcfg/token/serialize.go b/vendor/github.com/src-d/gcfg/token/serialize.go
new file mode 100644
index 00000000..4adc8f9e
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/token/serialize.go
@@ -0,0 +1,56 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package token
+
+type serializedFile struct {
+	// fields correspond 1:1 to fields with same (lower-case) name in File
+	Name  string
+	Base  int
+	Size  int
+	Lines []int
+	Infos []lineInfo
+}
+
+type serializedFileSet struct {
+	Base  int
+	Files []serializedFile
+}
+
+// Read calls decode to deserialize a file set into s; s must not be nil.
+func (s *FileSet) Read(decode func(interface{}) error) error {
+	var ss serializedFileSet
+	if err := decode(&ss); err != nil {
+		return err
+	}
+
+	s.mutex.Lock()
+	s.base = ss.Base
+	files := make([]*File, len(ss.Files))
+	for i := 0; i < len(ss.Files); i++ {
+		f := &ss.Files[i]
+		files[i] = &File{s, f.Name, f.Base, f.Size, f.Lines, f.Infos}
+	}
+	s.files = files
+	s.last = nil
+	s.mutex.Unlock()
+
+	return nil
+}
+
+// Write calls encode to serialize the file set s.
+func (s *FileSet) Write(encode func(interface{}) error) error {
+	var ss serializedFileSet
+
+	s.mutex.Lock()
+	ss.Base = s.base
+	files := make([]serializedFile, len(s.files))
+	for i, f := range s.files {
+		files[i] = serializedFile{f.name, f.base, f.size, f.lines, f.infos}
+	}
+	ss.Files = files
+	s.mutex.Unlock()
+
+	return encode(ss)
+}
diff --git a/vendor/github.com/src-d/gcfg/token/token.go b/vendor/github.com/src-d/gcfg/token/token.go
new file mode 100644
index 00000000..b3c7c83f
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/token/token.go
@@ -0,0 +1,83 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package token defines constants representing the lexical tokens of the gcfg
+// configuration syntax and basic operations on tokens (printing, predicates).
+//
+// Note that the API for the token package may change to accommodate new
+// features or implementation changes in gcfg.
+//
+package token
+
+import "strconv"
+
+// Token is the set of lexical tokens of the gcfg configuration syntax.
+type Token int
+
+// The list of tokens.
+const (
+	// Special tokens
+	ILLEGAL Token = iota
+	EOF
+	COMMENT
+
+	literal_beg
+	// Identifiers and basic type literals
+	// (these tokens stand for classes of literals)
+	IDENT  // section-name, variable-name
+	STRING // "subsection-name", variable value
+	literal_end
+
+	operator_beg
+	// Operators and delimiters
+	ASSIGN // =
+	LBRACK // [
+	RBRACK // ]
+	EOL    // \n
+	operator_end
+)
+
+var tokens = [...]string{
+	ILLEGAL: "ILLEGAL",
+
+	EOF:     "EOF",
+	COMMENT: "COMMENT",
+
+	IDENT:  "IDENT",
+	STRING: "STRING",
+
+	ASSIGN: "=",
+	LBRACK: "[",
+	RBRACK: "]",
+	EOL:    "\n",
+}
+
+// String returns the string corresponding to the token tok.
+// For operators and delimiters, the string is the actual token character
+// sequence (e.g., for the token ASSIGN, the string is "="). For all other
+// tokens the string corresponds to the token constant name (e.g. for the
+// token IDENT, the string is "IDENT").
+//
+func (tok Token) String() string {
+	s := ""
+	if 0 <= tok && tok < Token(len(tokens)) {
+		s = tokens[tok]
+	}
+	if s == "" {
+		s = "token(" + strconv.Itoa(int(tok)) + ")"
+	}
+	return s
+}
+
+// Predicates
+
+// IsLiteral returns true for tokens corresponding to identifiers
+// and basic type literals; it returns false otherwise.
+//
+func (tok Token) IsLiteral() bool { return literal_beg < tok && tok < literal_end }
+
+// IsOperator returns true for tokens corresponding to operators and
+// delimiters; it returns false otherwise.
+//
+func (tok Token) IsOperator() bool { return operator_beg < tok && tok < operator_end }
diff --git a/vendor/github.com/src-d/gcfg/types/bool.go b/vendor/github.com/src-d/gcfg/types/bool.go
new file mode 100644
index 00000000..8dcae0d8
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/types/bool.go
@@ -0,0 +1,23 @@
+package types
+
+// BoolValues defines the name and value mappings for ParseBool.
+var BoolValues = map[string]interface{}{
+	"true": true, "yes": true, "on": true, "1": true,
+	"false": false, "no": false, "off": false, "0": false,
+}
+
+var boolParser = func() *EnumParser {
+	ep := &EnumParser{}
+	ep.AddVals(BoolValues)
+	return ep
+}()
+
+// ParseBool parses bool values according to the definitions in BoolValues.
+// Parsing is case-insensitive.
+func ParseBool(s string) (bool, error) {
+	v, err := boolParser.Parse(s)
+	if err != nil {
+		return false, err
+	}
+	return v.(bool), nil
+}
diff --git a/vendor/github.com/src-d/gcfg/types/doc.go b/vendor/github.com/src-d/gcfg/types/doc.go
new file mode 100644
index 00000000..9f9c345f
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/types/doc.go
@@ -0,0 +1,4 @@
+// Package types defines helpers for type conversions.
+//
+// The API for this package is not finalized yet.
+package types
diff --git a/vendor/github.com/src-d/gcfg/types/enum.go b/vendor/github.com/src-d/gcfg/types/enum.go
new file mode 100644
index 00000000..1a0c7ef4
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/types/enum.go
@@ -0,0 +1,44 @@
+package types
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// EnumParser parses "enum" values; i.e. a predefined set of strings to
+// predefined values.
+type EnumParser struct {
+	Type      string // type name; if not set, use type of first value added
+	CaseMatch bool   // if true, matching of strings is case-sensitive
+	// PrefixMatch bool
+	vals map[string]interface{}
+}
+
+// AddVals adds strings and values to an EnumParser.
+func (ep *EnumParser) AddVals(vals map[string]interface{}) {
+	if ep.vals == nil {
+		ep.vals = make(map[string]interface{})
+	}
+	for k, v := range vals {
+		if ep.Type == "" {
+			ep.Type = reflect.TypeOf(v).Name()
+		}
+		if !ep.CaseMatch {
+			k = strings.ToLower(k)
+		}
+		ep.vals[k] = v
+	}
+}
+
+// Parse parses the string and returns the value or an error.
+func (ep EnumParser) Parse(s string) (interface{}, error) {
+	if !ep.CaseMatch {
+		s = strings.ToLower(s)
+	}
+	v, ok := ep.vals[s]
+	if !ok {
+		return false, fmt.Errorf("failed to parse %s %#q", ep.Type, s)
+	}
+	return v, nil
+}
diff --git a/vendor/github.com/src-d/gcfg/types/int.go b/vendor/github.com/src-d/gcfg/types/int.go
new file mode 100644
index 00000000..af7e75c1
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/types/int.go
@@ -0,0 +1,86 @@
+package types
+
+import (
+	"fmt"
+	"strings"
+)
+
+// An IntMode is a mode for parsing integer values, representing a set of
+// accepted bases.
+type IntMode uint8
+
+// IntMode values for ParseInt; can be combined using binary or.
+const (
+	Dec IntMode = 1 << iota
+	Hex
+	Oct
+)
+
+// String returns a string representation of IntMode; e.g. `IntMode(Dec|Hex)`.
+func (m IntMode) String() string {
+	var modes []string
+	if m&Dec != 0 {
+		modes = append(modes, "Dec")
+	}
+	if m&Hex != 0 {
+		modes = append(modes, "Hex")
+	}
+	if m&Oct != 0 {
+		modes = append(modes, "Oct")
+	}
+	return "IntMode(" + strings.Join(modes, "|") + ")"
+}
+
+var errIntAmbig = fmt.Errorf("ambiguous integer value; must include '0' prefix")
+
+func prefix0(val string) bool {
+	return strings.HasPrefix(val, "0") || strings.HasPrefix(val, "-0")
+}
+
+func prefix0x(val string) bool {
+	return strings.HasPrefix(val, "0x") || strings.HasPrefix(val, "-0x")
+}
+
+// ParseInt parses val using mode into intptr, which must be a pointer to an
+// integer kind type. Non-decimal value require prefix `0` or `0x` in the cases
+// when mode permits ambiguity of base; otherwise the prefix can be omitted.
+func ParseInt(intptr interface{}, val string, mode IntMode) error {
+	val = strings.TrimSpace(val)
+	verb := byte(0)
+	switch mode {
+	case Dec:
+		verb = 'd'
+	case Dec + Hex:
+		if prefix0x(val) {
+			verb = 'v'
+		} else {
+			verb = 'd'
+		}
+	case Dec + Oct:
+		if prefix0(val) && !prefix0x(val) {
+			verb = 'v'
+		} else {
+			verb = 'd'
+		}
+	case Dec + Hex + Oct:
+		verb = 'v'
+	case Hex:
+		if prefix0x(val) {
+			verb = 'v'
+		} else {
+			verb = 'x'
+		}
+	case Oct:
+		verb = 'o'
+	case Hex + Oct:
+		if prefix0(val) {
+			verb = 'v'
+		} else {
+			return errIntAmbig
+		}
+	}
+	if verb == 0 {
+		panic("unsupported mode")
+	}
+	return ScanFully(intptr, val, verb)
+}
diff --git a/vendor/github.com/src-d/gcfg/types/scan.go b/vendor/github.com/src-d/gcfg/types/scan.go
new file mode 100644
index 00000000..db2f6ed3
--- /dev/null
+++ b/vendor/github.com/src-d/gcfg/types/scan.go
@@ -0,0 +1,23 @@
+package types
+
+import (
+	"fmt"
+	"io"
+	"reflect"
+)
+
+// ScanFully uses fmt.Sscanf with verb to fully scan val into ptr.
+func ScanFully(ptr interface{}, val string, verb byte) error {
+	t := reflect.ValueOf(ptr).Elem().Type()
+	// attempt to read extra bytes to make sure the value is consumed
+	var b []byte
+	n, err := fmt.Sscanf(val, "%"+string(verb)+"%s", ptr, &b)
+	switch {
+	case n < 1 || n == 1 && err != io.EOF:
+		return fmt.Errorf("failed to parse %q as %v: %v", val, t, err)
+	case n > 1:
+		return fmt.Errorf("failed to parse %q as %v: extra characters %q", val, t, string(b))
+	}
+	// n == 1 && err == io.EOF
+	return nil
+}
diff --git a/vendor/github.com/xanzy/ssh-agent/.gitignore b/vendor/github.com/xanzy/ssh-agent/.gitignore
new file mode 100644
index 00000000..daf913b1
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/.gitignore
@@ -0,0 +1,24 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof
diff --git a/vendor/github.com/xanzy/ssh-agent/LICENSE b/vendor/github.com/xanzy/ssh-agent/LICENSE
new file mode 100644
index 00000000..8f71f43f
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/LICENSE
@@ -0,0 +1,202 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
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+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "{}"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright {yyyy} {name of copyright owner}
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
diff --git a/vendor/github.com/xanzy/ssh-agent/README.md b/vendor/github.com/xanzy/ssh-agent/README.md
new file mode 100644
index 00000000..d93af40a
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/README.md
@@ -0,0 +1,23 @@
+# ssh-agent
+
+Create a new [agent.Agent](https://godoc.org/golang.org/x/crypto/ssh/agent#Agent) on any type of OS (so including Windows) from any [Go](https://golang.org) application.
+
+## Limitations
+
+When compiled for Windows, it will only support [Pageant](http://the.earth.li/~sgtatham/putty/0.66/htmldoc/Chapter9.html#pageant) as the SSH authentication agent.
+
+## Credits
+
+Big thanks to [Давид Мзареулян (David Mzareulyan)](https://github.com/davidmz) for creating the [go-pageant](https://github.com/davidmz/go-pageant) package!
+
+## Issues
+
+If you have an issue: report it on the [issue tracker](https://github.com/xanzy/ssh-agent/issues)
+
+## Author
+
+Sander van Harmelen (<sander@xanzy.io>)
+
+## License
+
+The files `pageant_windows.go` and `sshagent_windows.go` have their own license (see file headers). The rest of this package is licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at <http://www.apache.org/licenses/LICENSE-2.0>
diff --git a/vendor/github.com/xanzy/ssh-agent/go.mod b/vendor/github.com/xanzy/ssh-agent/go.mod
new file mode 100644
index 00000000..6664c488
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/go.mod
@@ -0,0 +1,6 @@
+module github.com/xanzy/ssh-agent
+
+require (
+	golang.org/x/crypto v0.0.0-20190219172222-a4c6cb3142f2
+	golang.org/x/sys v0.0.0-20190221075227-b4e8571b14e0 // indirect
+)
diff --git a/vendor/github.com/xanzy/ssh-agent/go.sum b/vendor/github.com/xanzy/ssh-agent/go.sum
new file mode 100644
index 00000000..a9a00169
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/go.sum
@@ -0,0 +1,4 @@
+golang.org/x/crypto v0.0.0-20190219172222-a4c6cb3142f2 h1:NwxKRvbkH5MsNkvOtPZi3/3kmI8CAzs3mtv+GLQMkNo=
+golang.org/x/crypto v0.0.0-20190219172222-a4c6cb3142f2/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
+golang.org/x/sys v0.0.0-20190221075227-b4e8571b14e0 h1:bzeyCHgoAyjZjAhvTpks+qM7sdlh4cCSitmXeCEO3B4=
+golang.org/x/sys v0.0.0-20190221075227-b4e8571b14e0/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
diff --git a/vendor/github.com/xanzy/ssh-agent/pageant_windows.go b/vendor/github.com/xanzy/ssh-agent/pageant_windows.go
new file mode 100644
index 00000000..62956079
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/pageant_windows.go
@@ -0,0 +1,146 @@
+//
+// Copyright (c) 2014 David Mzareulyan
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+// and associated documentation files (the "Software"), to deal in the Software without restriction,
+// including without limitation the rights to use, copy, modify, merge, publish, distribute,
+// sublicense, and/or sell copies of the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial
+// portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+// BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+// +build windows
+
+package sshagent
+
+// see https://github.com/Yasushi/putty/blob/master/windows/winpgntc.c#L155
+// see https://github.com/paramiko/paramiko/blob/master/paramiko/win_pageant.py
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"sync"
+	"syscall"
+	"unsafe"
+)
+
+// Maximum size of message can be sent to pageant
+const MaxMessageLen = 8192
+
+var (
+	ErrPageantNotFound = errors.New("pageant process not found")
+	ErrSendMessage     = errors.New("error sending message")
+
+	ErrMessageTooLong       = errors.New("message too long")
+	ErrInvalidMessageFormat = errors.New("invalid message format")
+	ErrResponseTooLong      = errors.New("response too long")
+)
+
+const (
+	agentCopydataID = 0x804e50ba
+	wmCopydata      = 74
+)
+
+type copyData struct {
+	dwData uintptr
+	cbData uint32
+	lpData unsafe.Pointer
+}
+
+var (
+	lock sync.Mutex
+
+	winFindWindow         = winAPI("user32.dll", "FindWindowW")
+	winGetCurrentThreadID = winAPI("kernel32.dll", "GetCurrentThreadId")
+	winSendMessage        = winAPI("user32.dll", "SendMessageW")
+)
+
+func winAPI(dllName, funcName string) func(...uintptr) (uintptr, uintptr, error) {
+	proc := syscall.MustLoadDLL(dllName).MustFindProc(funcName)
+	return func(a ...uintptr) (uintptr, uintptr, error) { return proc.Call(a...) }
+}
+
+// Available returns true if Pageant is running
+func Available() bool { return pageantWindow() != 0 }
+
+// Query sends message msg to Pageant and returns response or error.
+// 'msg' is raw agent request with length prefix
+// Response is raw agent response with length prefix
+func query(msg []byte) ([]byte, error) {
+	if len(msg) > MaxMessageLen {
+		return nil, ErrMessageTooLong
+	}
+
+	msgLen := binary.BigEndian.Uint32(msg[:4])
+	if len(msg) != int(msgLen)+4 {
+		return nil, ErrInvalidMessageFormat
+	}
+
+	lock.Lock()
+	defer lock.Unlock()
+
+	paWin := pageantWindow()
+
+	if paWin == 0 {
+		return nil, ErrPageantNotFound
+	}
+
+	thID, _, _ := winGetCurrentThreadID()
+	mapName := fmt.Sprintf("PageantRequest%08x", thID)
+	pMapName, _ := syscall.UTF16PtrFromString(mapName)
+
+	mmap, err := syscall.CreateFileMapping(syscall.InvalidHandle, nil, syscall.PAGE_READWRITE, 0, MaxMessageLen+4, pMapName)
+	if err != nil {
+		return nil, err
+	}
+	defer syscall.CloseHandle(mmap)
+
+	ptr, err := syscall.MapViewOfFile(mmap, syscall.FILE_MAP_WRITE, 0, 0, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer syscall.UnmapViewOfFile(ptr)
+
+	mmSlice := (*(*[MaxMessageLen]byte)(unsafe.Pointer(ptr)))[:]
+
+	copy(mmSlice, msg)
+
+	mapNameBytesZ := append([]byte(mapName), 0)
+
+	cds := copyData{
+		dwData: agentCopydataID,
+		cbData: uint32(len(mapNameBytesZ)),
+		lpData: unsafe.Pointer(&(mapNameBytesZ[0])),
+	}
+
+	resp, _, _ := winSendMessage(paWin, wmCopydata, 0, uintptr(unsafe.Pointer(&cds)))
+
+	if resp == 0 {
+		return nil, ErrSendMessage
+	}
+
+	respLen := binary.BigEndian.Uint32(mmSlice[:4])
+	if respLen > MaxMessageLen-4 {
+		return nil, ErrResponseTooLong
+	}
+
+	respData := make([]byte, respLen+4)
+	copy(respData, mmSlice)
+
+	return respData, nil
+}
+
+func pageantWindow() uintptr {
+	nameP, _ := syscall.UTF16PtrFromString("Pageant")
+	h, _, _ := winFindWindow(uintptr(unsafe.Pointer(nameP)), uintptr(unsafe.Pointer(nameP)))
+	return h
+}
diff --git a/vendor/github.com/xanzy/ssh-agent/sshagent.go b/vendor/github.com/xanzy/ssh-agent/sshagent.go
new file mode 100644
index 00000000..259fea2b
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/sshagent.go
@@ -0,0 +1,49 @@
+//
+// Copyright 2015, Sander van Harmelen
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// +build !windows
+
+package sshagent
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"os"
+
+	"golang.org/x/crypto/ssh/agent"
+)
+
+// New returns a new agent.Agent that uses a unix socket
+func New() (agent.Agent, net.Conn, error) {
+	if !Available() {
+		return nil, nil, errors.New("SSH agent requested but SSH_AUTH_SOCK not-specified")
+	}
+
+	sshAuthSock := os.Getenv("SSH_AUTH_SOCK")
+
+	conn, err := net.Dial("unix", sshAuthSock)
+	if err != nil {
+		return nil, nil, fmt.Errorf("Error connecting to SSH_AUTH_SOCK: %v", err)
+	}
+
+	return agent.NewClient(conn), conn, nil
+}
+
+// Available returns true is a auth socket is defined
+func Available() bool {
+	return os.Getenv("SSH_AUTH_SOCK") != ""
+}
diff --git a/vendor/github.com/xanzy/ssh-agent/sshagent_windows.go b/vendor/github.com/xanzy/ssh-agent/sshagent_windows.go
new file mode 100644
index 00000000..c46710e8
--- /dev/null
+++ b/vendor/github.com/xanzy/ssh-agent/sshagent_windows.go
@@ -0,0 +1,80 @@
+//
+// Copyright (c) 2014 David Mzareulyan
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+// and associated documentation files (the "Software"), to deal in the Software without restriction,
+// including without limitation the rights to use, copy, modify, merge, publish, distribute,
+// sublicense, and/or sell copies of the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial
+// portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+// BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+// +build windows
+
+package sshagent
+
+import (
+	"errors"
+	"io"
+	"net"
+	"sync"
+
+	"golang.org/x/crypto/ssh/agent"
+)
+
+// New returns a new agent.Agent and the (custom) connection it uses
+// to communicate with a running pagent.exe instance (see README.md)
+func New() (agent.Agent, net.Conn, error) {
+	if !Available() {
+		return nil, nil, errors.New("SSH agent requested but Pageant not running")
+	}
+
+	return agent.NewClient(&conn{}), nil, nil
+}
+
+type conn struct {
+	sync.Mutex
+	buf []byte
+}
+
+func (c *conn) Close() {
+	c.Lock()
+	defer c.Unlock()
+	c.buf = nil
+}
+
+func (c *conn) Write(p []byte) (int, error) {
+	c.Lock()
+	defer c.Unlock()
+
+	resp, err := query(p)
+	if err != nil {
+		return 0, err
+	}
+
+	c.buf = append(c.buf, resp...)
+
+	return len(p), nil
+}
+
+func (c *conn) Read(p []byte) (int, error) {
+	c.Lock()
+	defer c.Unlock()
+
+	if len(c.buf) == 0 {
+		return 0, io.EOF
+	}
+
+	n := copy(p, c.buf)
+	c.buf = c.buf[n:]
+
+	return n, nil
+}