test-reach: test is_descendant_of

The is_descendant_of method takes a single commit as its first parameter
and a list of commits as its second parameter. Extend the input of the
'test-tool reach' command to take multiple lines of the form
"X:<committish>" to construct a list of commits. Pass these to
is_descendant_of and create tests that check each result.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/helper/test-reach.c

@@ -10,6 +10,7 @@ int cmd__reach(int ac, const char **av)
 {
 	struct object_id oid_A, oid_B;
 	struct commit *A, *B;
+	struct commit_list *X;
 	struct strbuf buf = STRBUF_INIT;
 	struct repository *r = the_repository;
 
@@ -19,6 +20,7 @@ int cmd__reach(int ac, const char **av)
 		exit(1);
 
 	A = B = NULL;
+	X = NULL;
 
 	while (strbuf_getline(&buf, stdin) != EOF) {
 		struct object_id oid;
@@ -54,6 +56,10 @@ int cmd__reach(int ac, const char **av)
 				B = c;
 				break;
 
+			case 'X':
+				commit_list_insert(c, &X);
+				break;
+
 			default:
 				die("unexpected start of line: %c", buf.buf[0]);
 		}
@@ -64,6 +70,8 @@ int cmd__reach(int ac, const char **av)
 		printf("%s(A,B):%d\n", av[1], ref_newer(&oid_A, &oid_B));
 	else if (!strcmp(av[1], "in_merge_bases"))
 		printf("%s(A,B):%d\n", av[1], in_merge_bases(A, B));
+	else if (!strcmp(av[1], "is_descendant_of"))
+		printf("%s(A,X):%d\n", av[1], is_descendant_of(A, X));
 
 	exit(0);
 }

t/t6600-test-reach.sh

@@ -101,4 +101,26 @@ test_expect_success 'in_merge_bases:miss' '
 	test_three_modes in_merge_bases
 '
 
+test_expect_success 'is_descendant_of:hit' '
+	cat >input <<-\EOF &&
+	A:commit-5-7
+	X:commit-4-8
+	X:commit-6-6
+	X:commit-1-1
+	EOF
+	echo "is_descendant_of(A,X):1" >expect &&
+	test_three_modes is_descendant_of
+'
+
+test_expect_success 'is_descendant_of:miss' '
+	cat >input <<-\EOF &&
+	A:commit-6-8
+	X:commit-5-9
+	X:commit-4-10
+	X:commit-7-6
+	EOF
+	echo "is_descendant_of(A,X):0" >expect &&
+	test_three_modes is_descendant_of
+'
+
 test_done