diff --check: detect leftover conflict markers

This teaches "diff --check" to detect and complain if the change
adds lines that look like leftover conflict markers.

We should be able to remove the old Perl script used in the sample
pre-commit hook and modernize the script with this facility.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/t/t4017-diff-retval.sh b/t/t4017-diff-retval.sh
index 0d0fb87f57..d748d45dae 100755
--- a/t/t4017-diff-retval.sh
+++ b/t/t4017-diff-retval.sh
@@ -113,4 +113,18 @@ test_expect_success 'check should test not just the last line' '
 
 '
 
+test_expect_success 'check detects leftover conflict markers' '
+	git reset --hard &&
+	git checkout HEAD^ &&
+	echo binary >>b &&
+	git commit -m "side" b &&
+	test_must_fail git merge master &&
+	git add b && (
+		git --no-pager diff --cached --check >test.out
+		test $? = 2
+	) &&
+	test "$(grep "conflict marker" test.out | wc -l)" = 3 &&
+	git reset --hard
+'
+
 test_done