rebase: use correct base for --keep-base when a branch is given

--keep-base rebases onto the merge base of the given upstream and the
current HEAD regardless of whether a branch is given. This is contrary
to the documentation and to the option's intended purpose. Instead,
rebase onto the merge base of the given upstream and the given branch.

Signed-off-by: Alex Henrie <alexhenrie24@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/t/t3416-rebase-onto-threedots.sh b/t/t3416-rebase-onto-threedots.sh
index 3716a42e81..3e04802cb0 100755
--- a/t/t3416-rebase-onto-threedots.sh
+++ b/t/t3416-rebase-onto-threedots.sh
@@ -129,6 +129,20 @@ test_expect_success 'rebase --keep-base main from topic' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rebase --keep-base main topic from main' '
+	git checkout main &&
+	git branch -f topic G &&
+
+	git rebase --keep-base main topic &&
+	git rev-parse C >base.expect &&
+	git merge-base main HEAD >base.actual &&
+	test_cmp base.expect base.actual &&
+
+	git rev-parse HEAD~2 >actual &&
+	git rev-parse C^0 >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'rebase --keep-base main from side' '
 	git reset --hard &&
 	git checkout side &&
@@ -153,6 +167,21 @@ test_expect_success 'rebase -i --keep-base main from topic' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rebase -i --keep-base main topic from main' '
+	git checkout main &&
+	git branch -f topic G &&
+
+	set_fake_editor &&
+	EXPECT_COUNT=2 git rebase -i --keep-base main topic &&
+	git rev-parse C >base.expect &&
+	git merge-base main HEAD >base.actual &&
+	test_cmp base.expect base.actual &&
+
+	git rev-parse HEAD~2 >actual &&
+	git rev-parse C^0 >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'rebase -i --keep-base main from side' '
 	git reset --hard &&
 	git checkout side &&