bug#1537: diff-mode for git patches trouble

[Dmitriy Blinov]

There is the problem then I'm trying to edit git-generated patches in 
emacs diff-mode.

git patches look like:
---
hello.txt |    2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/hello.txt b/hello.txt
index 55bf894..25a09cc 100644
--- a/hello.txt
+++ b/hello.txt
@@ -6,7 +6,7 @@
5
6
7
-8
+8 8
9
10
11
--
1.5.6.5


The last but one line is two minuses by default. And diff-mode 
recognizes  first minus as  deleted  string.
Therefore  when we change some strings in patch, emacs creates malformed 
hunk offset.
It will be @@ -6,8 +6,7 @@ insead of correct @@ -6,7 +6,7 @@ after patch 
edition (if we don't delete/create strings).

Is it possible to fix this harm or I should append whitespace before 
"--" string  always?