[PATCH 1/2] diff: add test for --no-index executed outside repo

[Thomas Gummerer <t.gummerer@gmail.com>]

470faf9 diff: move no-index detection to builtin/diff.c breaks the error
message for "git diff --no-index", when the command is executed outside
of a git repository and the wrong number of arguments are given. 6df5762
diff: don't read index when --no-index is given fixes the problem.

Add a test to guard against similar breakages in the future.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
---

>> Thanks, I've missed that one.  It only happens when run outside a git
>> repository, but the same  comments still apply.  Will fix and send a
>> re-roll.
>
> Please don't, as the last round has already been pushed on 'next'.

Sorry about that, should have checked first.

> An incremental change on top would also illustrate more clearly what
> breakage needed to be fixed, which would be another good thing. It
> could even come with a new test that makes sure that the above
> command line is diagnosed correctly as a mistake ;-).

The breakage is actually fixed with the second patch as described in
the commit message above, so here is just a test against future
breakages.  This test only works when the test root is outside of a
git repository, as otherwise nongit will not be set.  Is there another
way to write it?

t/t4053-diff-no-index.sh | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/t/t4053-diff-no-index.sh b/t/t4053-diff-no-index.sh
index 077c775..eb4f380 100755
--- a/t/t4053-diff-no-index.sh
+++ b/t/t4053-diff-no-index.sh
@@ -44,4 +44,11 @@ test_expect_success 'git diff outside repo with broken index' '
 	)
 '
 
+test_expect_success 'git diff --no-index executed outside repo gives correct error message' '
+	rm -rf .git &&
+	test_must_fail git diff --no-index a b b 2>actual.err &&
+	echo "usage: git diff --no-index <path> <path>" >expect.err &&
+	test_cmp expect.err actual.err
+'
+
 test_done
-- 
1.8.5.4.g8639e57