Make diffcore_std only can run once before a diff_flush

When file renames/copies detection is turned on, the
second diffcore_std will degrade a 'C' pair to a 'R' pair.

And this may happen when we run 'git log --follow' with
hard copies finding. That is, the try_to_follow_renames()
will run diffcore_std to find the copies, and then
'git log' will issue another diffcore_std, which will reduce
'src->rename_used' and recognize this copy as a rename.
This is not what we want.

So, I think we really don't need to run diffcore_std more
than one time.

Signed-off-by: Bo Yang <struggleyb.nku@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/diff.c b/diff.c
index 4a350e3..f0985bc 100644
--- a/diff.c
+++ b/diff.c
@@ -3737,6 +3737,12 @@ void diffcore_fix_diff_index(struct diff_options *options)
 
 void diffcore_std(struct diff_options *options)
 {
+	/* We never run this function more than one time, because the
+	 * rename/copy detection logic can only run once.
+	 */
+	if (diff_queued_diff.run)
+		return;
+
 	if (options->skip_stat_unmatch)
 		diffcore_skip_stat_unmatch(options);
 	if (options->break_opt != -1)
@@ -3756,6 +3762,8 @@ void diffcore_std(struct diff_options *options)
 		DIFF_OPT_SET(options, HAS_CHANGES);
 	else
 		DIFF_OPT_CLR(options, HAS_CHANGES);
+
+	diff_queued_diff.run = 1;
 }
 
 int diff_result_code(struct diff_options *opt, int status)