1 files changed, 262 insertions, 0 deletions
diff --git a/builtin/merge-base.c b/builtin/merge-base.c
new file mode 100644
index 0000000000..cfe2a796f8
--- /dev/null
+++ b/builtin/merge-base.c
@@ -0,0 +1,262 @@
+#include "builtin.h"
+#include "cache.h"
+#include "commit.h"
+#include "refs.h"
+#include "diff.h"
+#include "revision.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_dirty(rev[0], rev_nr - 1, rev + 1);
+
+	if (!result)
+		return 1;
+
+	while (result) {
+		printf("%s\n", oid_to_hex(&result->item->object.oid));
+		if (!show_all)
+			return 0;
+		result = result->next;
+	}
+
+	return 0;
+}
+
+static const char * const merge_base_usage[] = {
+	N_("git merge-base [-a | --all] <commit> <commit>..."),
+	N_("git merge-base [-a | --all] --octopus <commit>..."),
+	N_("git merge-base --independent <commit>..."),
+	N_("git merge-base --is-ancestor <commit> <commit>"),
+	N_("git merge-base --fork-point <ref> [<commit>]"),
+	NULL
+};
+
+static struct commit *get_commit_reference(const char *arg)
+{
+	struct object_id revkey;
+	struct commit *r;
+
+	if (get_oid(arg, &revkey))
+		die("Not a valid object name %s", arg);
+	r = lookup_commit_reference(revkey.hash);
+	if (!r)
+		die("Not a valid commit name %s", arg);
+
+	return r;
+}
+
+static int handle_independent(int count, const char **args)
+{
+	struct commit_list *revs = NULL;
+	struct commit_list *result;
+	int i;
+
+	for (i = count - 1; i >= 0; i--)
+		commit_list_insert(get_commit_reference(args[i]), &revs);
+
+	result = reduce_heads(revs);
+	if (!result)
+		return 1;
+
+	while (result) {
+		printf("%s\n", oid_to_hex(&result->item->object.oid));
+		result = result->next;
+	}
+	return 0;
+}
+
+static int handle_octopus(int count, const char **args, int show_all)
+{
+	struct commit_list *revs = NULL;
+	struct commit_list *result;
+	int i;
+
+	for (i = count - 1; i >= 0; i--)
+		commit_list_insert(get_commit_reference(args[i]), &revs);
+
+	result = reduce_heads(get_octopus_merge_bases(revs));
+
+	if (!result)
+		return 1;
+
+	while (result) {
+		printf("%s\n", oid_to_hex(&result->item->object.oid));
+		if (!show_all)
+			return 0;
+		result = result->next;
+	}
+
+	return 0;
+}
+
+static int handle_is_ancestor(int argc, const char **argv)
+{
+	struct commit *one, *two;
+
+	if (argc != 2)
+		die("--is-ancestor takes exactly two commits");
+	one = get_commit_reference(argv[0]);
+	two = get_commit_reference(argv[1]);
+	if (in_merge_bases(one, two))
+		return 0;
+	else
+		return 1;
+}
+
+struct rev_collect {
+	struct commit **commit;
+	int nr;
+	int alloc;
+	unsigned int initial : 1;
+};
+
+static void add_one_commit(struct object_id *oid, struct rev_collect *revs)
+{
+	struct commit *commit;
+
+	if (is_null_oid(oid))
+		return;
+
+	commit = lookup_commit(oid->hash);
+	if (!commit ||
+	    (commit->object.flags & TMP_MARK) ||
+	    parse_commit(commit))
+		return;
+
+	ALLOC_GROW(revs->commit, revs->nr + 1, revs->alloc);
+	revs->commit[revs->nr++] = commit;
+	commit->object.flags |= TMP_MARK;
+}
+
+static int collect_one_reflog_ent(struct object_id *ooid, struct object_id *noid,
+				  const char *ident, unsigned long timestamp,
+				  int tz, const char *message, void *cbdata)
+{
+	struct rev_collect *revs = cbdata;
+
+	if (revs->initial) {
+		revs->initial = 0;
+		add_one_commit(ooid, revs);
+	}
+	add_one_commit(noid, revs);
+	return 0;
+}
+
+static int handle_fork_point(int argc, const char **argv)
+{
+	struct object_id oid;
+	char *refname;
+	const char *commitname;
+	struct rev_collect revs;
+	struct commit *derived;
+	struct commit_list *bases;
+	int i, ret = 0;
+
+	switch (dwim_ref(argv[0], strlen(argv[0]), oid.hash, &refname)) {
+	case 0:
+		die("No such ref: '%s'", argv[0]);
+	case 1:
+		break; /* good */
+	default:
+		die("Ambiguous refname: '%s'", argv[0]);
+	}
+
+	commitname = (argc == 2) ? argv[1] : "HEAD";
+	if (get_oid(commitname, &oid))
+		die("Not a valid object name: '%s'", commitname);
+
+	derived = lookup_commit_reference(oid.hash);
+	memset(&revs, 0, sizeof(revs));
+	revs.initial = 1;
+	for_each_reflog_ent(refname, collect_one_reflog_ent, &revs);
+
+	if (!revs.nr && !get_oid(refname, &oid))
+		add_one_commit(&oid, &revs);
+
+	for (i = 0; i < revs.nr; i++)
+		revs.commit[i]->object.flags &= ~TMP_MARK;
+
+	bases = get_merge_bases_many_dirty(derived, revs.nr, revs.commit);
+
+	/*
+	 * There should be one and only one merge base, when we found
+	 * a common ancestor among reflog entries.
+	 */
+	if (!bases || bases->next) {
+		ret = 1;
+		goto cleanup_return;
+	}
+
+	/* And the found one must be one of the reflog entries */
+	for (i = 0; i < revs.nr; i++)
+		if (&bases->item->object == &revs.commit[i]->object)
+			break; /* found */
+	if (revs.nr <= i) {
+		ret = 1; /* not found */
+		goto cleanup_return;
+	}
+
+	printf("%s\n", oid_to_hex(&bases->item->object.oid));
+
+cleanup_return:
+	free_commit_list(bases);
+	return ret;
+}
+
+int cmd_merge_base(int argc, const char **argv, const char *prefix)
+{
+	struct commit **rev;
+	int rev_nr = 0;
+	int show_all = 0;
+	int cmdmode = 0;
+
+	struct option options[] = {
+		OPT_BOOL('a', "all", &show_all, N_("output all common ancestors")),
+		OPT_CMDMODE(0, "octopus", &cmdmode,
+			    N_("find ancestors for a single n-way merge"), 'o'),
+		OPT_CMDMODE(0, "independent", &cmdmode,
+			    N_("list revs not reachable from others"), 'r'),
+		OPT_CMDMODE(0, "is-ancestor", &cmdmode,
+			    N_("is the first one ancestor of the other?"), 'a'),
+		OPT_CMDMODE(0, "fork-point", &cmdmode,
+			    N_("find where <commit> forked from reflog of <ref>"), 'f'),
+		OPT_END()
+	};
+
+	git_config(git_default_config, NULL);
+	argc = parse_options(argc, argv, prefix, options, merge_base_usage, 0);
+
+	if (cmdmode == 'a') {
+		if (argc < 2)
+			usage_with_options(merge_base_usage, options);
+		if (show_all)
+			die("--is-ancestor cannot be used with --all");
+		return handle_is_ancestor(argc, argv);
+	}
+
+	if (cmdmode == 'r' && show_all)
+		die("--independent cannot be used with --all");
+
+	if (cmdmode == 'o')
+		return handle_octopus(argc, argv, show_all);
+
+	if (cmdmode == 'r')
+		return handle_independent(argc, argv);
+
+	if (cmdmode == 'f') {
+		if (argc < 1 || 2 < argc)
+			usage_with_options(merge_base_usage, options);
+		return handle_fork_point(argc, argv);
+	}
+
+	if (argc < 2)
+		usage_with_options(merge_base_usage, options);
+
+	ALLOC_ARRAY(rev, argc);
+	while (argc-- > 0)
+		rev[rev_nr++] = get_commit_reference(*argv++);
+	return show_merge_base(rev, rev_nr, show_all);
+}