rc tools patch: skip spurious diff header for files with no changes

Since :patch transforms its inputs into context-only lines, we can
easily get into a state where a file diff has only context lines.
git apply does not accept a "diff" without any hunk, so let's skip
that.

4 files changed, 32 insertions, 0 deletions

diff --git a/test/tools/patch/ignore-first-file/cmd b/test/tools/patch/ignore-first-file/cmd
new file mode 100644
index 00000000..2b5ac0b6
--- /dev/null
+++ b/test/tools/patch/ignore-first-file/cmd
@@ -0,0 +1 @@
+%:patch tee applied.diff<ret><ret>!echo Applied:; cat applied.diff; echo; echo Updated buffer:<ret>
diff --git a/test/tools/patch/ignore-first-file/in b/test/tools/patch/ignore-first-file/in
new file mode 100644
index 00000000..5738a9b9
--- /dev/null
+++ b/test/tools/patch/ignore-first-file/in
@@ -0,0 +1,11 @@
+diff -ur a/file1 b/file1
+--- a/file1
++++ b/file1
+@@ -1 +1 @@
+ file1 here
+diff -ur a/file2 b/file2
+--- a/file2
++++ b/file2
+@@ -1 +1 @@
+-file2 here
++modified file2 here
diff --git a/test/tools/patch/ignore-first-file/out b/test/tools/patch/ignore-first-file/out
new file mode 100644
index 00000000..11d3d3af
--- /dev/null
+++ b/test/tools/patch/ignore-first-file/out
@@ -0,0 +1,19 @@
+Applied:
+diff -ur a/file2 b/file2
+--- a/file2
++++ b/file2
+@@ -1 +1 @@
+-file2 here
++modified file2 here
+
+Updated buffer:
+diff -ur a/file1 b/file1
+--- a/file1
++++ b/file1
+@@ -1 +1 @@
+ file1 here
+diff -ur a/file2 b/file2
+--- a/file2
++++ b/file2
+@@ -1 +1 @@
+ modified file2 here
diff --git a/test/tools/patch/ignore-first-file/rc b/test/tools/patch/ignore-first-file/rc
new file mode 100644
index 00000000..62ee8585
--- /dev/null
+++ b/test/tools/patch/ignore-first-file/rc
@@ -0,0 +1 @@
+source "%val{runtime}/rc/tools/patch.kak"