[PATCH v2] Fix revision walk for commits with the same dates

[Kacper Kornet <draenog@pld-linux.org>]

Logic in still_interesting function allows to stop the commits
traversing if the oldest processed commit is not older then the
youngest commit on the list to process and the list contains only
commits marked as not interesting ones. It can be premature when dealing
with a set of coequal commits. For example git rev-list A^! --not B
provides wrong answer if all commits in the range A..B had the same
commit time and there are more then 7 of them.

To fix this problem the relevant part of the logic in still_interesting
is changed to: the walk can be stopped if the oldest processed commit is
younger then the youngest commit on the list to processed.

Signed-off-by: Kacper Kornet <draenog@pld-linux.org>
---

I don't know whether the first version was overlooked or deemed as not
worthy. So just in case I resend it. Changes since the first version:

1. The test has been added
2. The commit log has been rewritten


 revision.c                 |  2 +-
 t/t6009-rev-list-parent.sh | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/revision.c b/revision.c
index ef60205..cf620c6 100644
--- a/revision.c
+++ b/revision.c
@@ -709,7 +709,7 @@ static int still_interesting(struct commit_list *src, unsigned long date, int sl
 	 * Does the destination list contain entries with a date
 	 * before the source list? Definitely _not_ done.
 	 */
-	if (date < src->item->date)
+	if (date <= src->item->date)
 		return SLOP;
 
 	/*
diff --git a/t/t6009-rev-list-parent.sh b/t/t6009-rev-list-parent.sh
index 3050740..66cda17 100755
--- a/t/t6009-rev-list-parent.sh
+++ b/t/t6009-rev-list-parent.sh
@@ -133,4 +133,17 @@ test_expect_success 'dodecapus' '
 	check_revlist "--min-parents=13" &&
 	check_revlist "--min-parents=4 --max-parents=11" tetrapus
 '
+
+test_expect_success 'ancestors with the same commit time' '
+
+	test_tick_keep=$test_tick &&
+	for i in 1 2 3 4 5 6 7 8; do
+		test_tick=$test_tick_keep
+		test_commit t$i
+	done &&
+	git rev-list t1^! --not t$i >result &&
+	>expect &&
+	test_cmp expect result
+'
+
 test_done
-- 
1.8.2

-- 
  Kacper Kornet