1 files changed, 51 insertions, 0 deletions
diff --git a/builtin-merge-base.c b/builtin-merge-base.c
new file mode 100644
index 0000000000..e35d362f26
--- /dev/null
+++ b/builtin-merge-base.c
@@ -0,0 +1,51 @@
+#include "cache.h"
+#include "commit.h"
+
+static int show_merge_base(struct commit *rev1, struct commit *rev2, int show_all)
+{
+	struct commit_list *result = get_merge_bases(rev1, rev2, 0);
+
+	if (!result)
+		return 1;
+
+	while (result) {
+		printf("%s\n", sha1_to_hex(result->item->object.sha1));
+		if (!show_all)
+			return 0;
+		result = result->next;
+	}
+
+	return 0;
+}
+
+static const char merge_base_usage[] =
+"git-merge-base [--all] <commit-id> <commit-id>";
+
+int cmd_merge_base(int argc, const char **argv, const char *prefix)
+{
+	struct commit *rev1, *rev2;
+	unsigned char rev1key[20], rev2key[20];
+	int show_all = 0;
+
+	git_config(git_default_config);
+
+	while (1 < argc && argv[1][0] == '-') {
+		const char *arg = argv[1];
+		if (!strcmp(arg, "-a") || !strcmp(arg, "--all"))
+			show_all = 1;
+		else
+			usage(merge_base_usage);
+		argc--; argv++;
+	}
+	if (argc != 3)
+		usage(merge_base_usage);
+	if (get_sha1(argv[1], rev1key))
+		die("Not a valid object name %s", argv[1]);
+	if (get_sha1(argv[2], rev2key))
+		die("Not a valid object name %s", argv[2]);
+	rev1 = lookup_commit_reference(rev1key);
+	rev2 = lookup_commit_reference(rev2key);
+	if (!rev1 || !rev2)
+		return 1;
+	return show_merge_base(rev1, rev2, show_all);
+}