[PATCH] completion: complete "git diff ...branc<TAB>"

While doing a final sanity check before merging a topic Bsomething, it is
a good idea to review what damage Bsomething branch would make, by running:

    $ git diff ...Bsomething

I however find myself often typing "git diff ...B<TAB>", seeing nothing
happening and then repeatedly hitting <TAB>, saying "huh? <TAAAAAAAAB>!".

This change would hopefully help me, and others like me.

Even though there is no point in supporting "git diff A..B" (you can say
"git diff A B" just fine), but reusing complete-revlist was the easiest
and that form is supported as a benign but not so useful side effect.

Signed-off-by: Junio C Hamano <redacted>
---

 * I sent this out a while ago and have been using it ever since, but
   totally forgot about it.  Likes, dislikes, alternatives?

 contrib/completion/git-completion.bash |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 64341d5..cf56514 100755
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash

@@ -1137,7 +1137,7 @@ _git_diff ()
 		return
 		;;
 	esac
-	__git_complete_file
+	__git_complete_revlist
 }
 
 __git_mergetools_common="diffuse ecmerge emerge kdiff3 meld opendiff