revision: Turn off history simplification in --ancestry-path mode

When using --ancestry-path together with history simplification (typically
triggered by path limiting), history simplification would get in the way of
--ancestry-path by prematurely removing the parent links between commits on
which the ancestry path calculations are made.

This patch disables this history simplification when --ancestry-path is
enabled. This is similar to what e.g. --full-history already does.

The patch also includes a simple testcase verifying that --ancestry-path
works together with path limiting.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -1190,6 +1190,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->first_parent_only = 1;
 	} else if (!strcmp(arg, "--ancestry-path")) {
 		revs->ancestry_path = 1;
+		revs->simplify_history = 0;
 		revs->limited = 1;
 	} else if (!strcmp(arg, "-g") || !strcmp(arg, "--walk-reflogs")) {
 		init_reflog_walk(&revs->reflog_info);

t/t6019-rev-list-ancestry-path.sh

@@ -10,6 +10,9 @@ test_description='--ancestry-path'
 #
 #  D..M                 == E F G H I J K L M
 #  --ancestry-path D..M == E F H I J L M
+#
+#  D..M -- M.t                 == M
+#  --ancestry-path D..M -- M.t == M
 
 . ./test-lib.sh
 
@@ -53,4 +56,18 @@ test_expect_success 'rev-list --ancestry-path D..M' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rev-list D..M -- M.t' '
+	echo M >expect &&
+	git rev-list --format=%s D..M -- M.t |
+	sed -e "/^commit /d" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rev-list --ancestry-patch D..M -- M.t' '
+	echo M >expect &&
+	git rev-list --ancestry-path --format=%s D..M -- M.t |
+	sed -e "/^commit /d" >actual &&
+	test_cmp expect actual
+'
+
 test_done