Fix BufReadFifo overlapping range on partial line

As reported in [1], when reading from a fifo a buffer that is not
newline-terminated, we add a newline automatically, and include that
in the range reported to BufReadFifo.

I'm not 100% sure if this is really wrong but since the typical
consumer of BufReadFifo does something like

	select %val{hook_param}
	exec |grep foo<ret>

it seems safe to remove this newline; doing so means that
1. "grep foo" will no longer see a newline in stdin, which
   seems good.
2. Kakoune will strip a trailing newline from the command output,
   since the input didn't have one. So the input is the same.

Let's remove any artificially-added newline from the hook parameter.

[1]: https://lists.sr.ht/~mawww/kakoune/%3CZzXjfXnETd2gbeXa@thristian.org%3E

1 files changed, 4 insertions, 1 deletions

diff --git a/src/buffer_utils.cc b/src/buffer_utils.cc
index 9a46504d..5e55036c 100644
--- a/src/buffer_utils.cc
+++ b/src/buffer_utils.cc
@@ -258,9 +258,12 @@ Buffer* create_fifo_buffer(String name, int fd, Buffer::Flags flags, bool scroll
             }
 
             if (insert_begin)
+            {
+                auto insert_back = m_had_trailing_newline ? m_buffer.back_coord() : m_buffer.prev(m_buffer.back_coord());
                 m_buffer.run_hook_in_own_context(
                     Hook::BufReadFifo,
-                    selection_to_string(ColumnType::Byte, m_buffer, {*insert_begin, m_buffer.back_coord()}));
+                    selection_to_string(ColumnType::Byte, m_buffer, {*insert_begin, insert_back}));
+            }
 
             if (closed)
                 m_buffer.values().erase(fifo_watcher_id); // will delete this