rebase -i: demonstrate bugs with fixup!/squash! commit messages

When multiple fixup/squash commands are processed and the last one
causes merge conflicts and is skipped, we leave the "This is a
combination of ..." comments in the commit message.

Noticed by Eric Sunshine.

This regression test also demonstrates that we rely on the localized
version of

	# This is a combination of <number> commits

to contain the <number> in ASCII, which breaks under GETTEXT_POISON.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3418-rebase-continue.sh

@@ -88,6 +88,28 @@ test_expect_success 'rebase passes merge strategy options correctly' '
 	git rebase --continue
 '
 
+test_expect_failure '--skip after failed fixup cleans commit message' '
+	test_when_finished "test_might_fail git rebase --abort" &&
+	git checkout -b with-conflicting-fixup &&
+	test_commit wants-fixup &&
+	test_commit "fixup! wants-fixup" wants-fixup.t 1 wants-fixup-1 &&
+	test_commit "fixup! wants-fixup" wants-fixup.t 2 wants-fixup-2 &&
+	test_commit "fixup! wants-fixup" wants-fixup.t 3 wants-fixup-3 &&
+	test_must_fail env FAKE_LINES="1 fixup 2 fixup 4" \
+		git rebase -i HEAD~4 &&
+
+	: now there is a conflict, and comments in the commit message &&
+	git show HEAD >out &&
+	grep "fixup! wants-fixup" out &&
+
+	: skip and continue &&
+	git rebase --skip &&
+
+	: now the comments in the commit message should have been cleaned up &&
+	git show HEAD >out &&
+	! grep "fixup! wants-fixup" out
+'
+
 test_expect_success 'setup rerere database' '
 	rm -fr .git/rebase-* &&
 	git reset --hard commit-new-file-F3-on-topic-branch &&