1 files changed, 63 insertions, 0 deletions
diff --git a/builtin/merge-base.c b/builtin/merge-base.c
new file mode 100644
index 0000000000..54e7ec2237
--- /dev/null
+++ b/builtin/merge-base.c
@@ -0,0 +1,63 @@
+#include "builtin.h"
+#include "cache.h"
+#include "commit.h"
+#include "parse-options.h"
+
+static int show_merge_base(struct commit **rev, int rev_nr, int show_all)
+{
+	struct commit_list *result;
+
+	result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1, 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 * const merge_base_usage[] = {
+	"git merge-base [-a|--all] <commit> <commit>...",
+	NULL
+};
+
+static struct commit *get_commit_reference(const char *arg)
+{
+	unsigned char revkey[20];
+	struct commit *r;
+
+	if (get_sha1(arg, revkey))
+		die("Not a valid object name %s", arg);
+	r = lookup_commit_reference(revkey);
+	if (!r)
+		die("Not a valid commit name %s", arg);
+
+	return r;
+}
+
+int cmd_merge_base(int argc, const char **argv, const char *prefix)
+{
+	struct commit **rev;
+	int rev_nr = 0;
+	int show_all = 0;
+
+	struct option options[] = {
+		OPT_BOOLEAN('a', "all", &show_all, "outputs all common ancestors"),
+		OPT_END()
+	};
+
+	git_config(git_default_config, NULL);
+	argc = parse_options(argc, argv, prefix, options, merge_base_usage, 0);
+	if (argc < 2)
+		usage_with_options(merge_base_usage, options);
+	rev = xmalloc(argc * sizeof(*rev));
+	while (argc-- > 0)
+		rev[rev_nr++] = get_commit_reference(*argv++);
+	return show_merge_base(rev, rev_nr, show_all);
+}