test-reach: test get_merge_bases_many

The get_merge_bases_many method returns a list of merge bases for a
single commit (A) against a list of commits (X). Some care is needed in
constructing the expected behavior because the result is not the
expected merge-base for an octopus merge with those parents but instead
the set of maximal commits that are reachable from A and at least one of
the commits in X.

Add get_merge_bases_many to 'test-tool reach' and create a test that
demonstrates that this output returns multiple results. Specifically, we
select a list of three commits such that we output two commits that are
reachable from one of the first two, respectively, and none are
reachable from the third.

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

t/helper/test-reach.c

@@ -4,13 +4,34 @@
 #include "commit-reach.h"
 #include "config.h"
 #include "parse-options.h"
+#include "string-list.h"
 #include "tag.h"
 
+static void print_sorted_commit_ids(struct commit_list *list)
+{
+	int i;
+	struct string_list s = STRING_LIST_INIT_DUP;
+
+	while (list) {
+		string_list_append(&s, oid_to_hex(&list->item->object.oid));
+		list = list->next;
+	}
+
+	string_list_sort(&s);
+
+	for (i = 0; i < s.nr; i++)
+		printf("%s\n", s.items[i].string);
+
+	string_list_clear(&s, 0);
+}
+
 int cmd__reach(int ac, const char **av)
 {
 	struct object_id oid_A, oid_B;
 	struct commit *A, *B;
 	struct commit_list *X;
+	struct commit **X_array;
+	int X_nr, X_alloc;
 	struct strbuf buf = STRBUF_INIT;
 	struct repository *r = the_repository;
 
@@ -21,6 +42,9 @@ int cmd__reach(int ac, const char **av)
 
 	A = B = NULL;
 	X = NULL;
+	X_nr = 0;
+	X_alloc = 16;
+	ALLOC_ARRAY(X_array, X_alloc);
 
 	while (strbuf_getline(&buf, stdin) != EOF) {
 		struct object_id oid;
@@ -58,6 +82,8 @@ int cmd__reach(int ac, const char **av)
 
 			case 'X':
 				commit_list_insert(c, &X);
+				ALLOC_GROW(X_array, X_nr + 1, X_alloc);
+				X_array[X_nr++] = c;
 				break;
 
 			default:
@@ -72,6 +98,11 @@ int cmd__reach(int ac, const char **av)
 		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));
+	else if (!strcmp(av[1], "get_merge_bases_many")) {
+		struct commit_list *list = get_merge_bases_many(A, X_nr, X_array);
+		printf("%s(A,X):\n", av[1]);
+		print_sorted_commit_ids(list);
+	}
 
 	exit(0);
 }

t/t6600-test-reach.sh

@@ -123,4 +123,19 @@ test_expect_success 'is_descendant_of:miss' '
 	test_three_modes is_descendant_of
 '
 
+test_expect_success 'get_merge_bases_many' '
+	cat >input <<-\EOF &&
+	A:commit-5-7
+	X:commit-4-8
+	X:commit-6-6
+	X:commit-8-3
+	EOF
+	{
+		echo "get_merge_bases_many(A,X):" &&
+		git rev-parse commit-5-6 \
+			      commit-4-7 | sort
+	} >expect &&
+	test_three_modes get_merge_bases_many
+'
+
 test_done