refactor merge_bases() as preparation to libify merge-base

Signed-off-by: Junio C Hamano <junkio@cox.net>

merge-base.c

@@ -124,8 +124,6 @@ static struct commit *interesting(struct commit_list *list)
  * to contaminate D and E.
  */
 
-static int show_all = 0;
-
 static void mark_reachable_commits(struct commit_list *result,
 				   struct commit_list *list)
 {
@@ -167,34 +165,33 @@ static void mark_reachable_commits(struct commit_list *result,
 	}
 }
 
-static int merge_base(struct commit *rev1, struct commit *rev2)
+struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2)
 {
 	struct commit_list *list = NULL;
 	struct commit_list *result = NULL;
 	struct commit_list *tmp = NULL;
 
-	if (rev1 == rev2) {
-		printf("%s\n", sha1_to_hex(rev1->object.sha1));
-		return 0;
-	}
+	if (rev1 == rev2)
+		return commit_list_insert(rev1, &result);
 
 	parse_commit(rev1);
 	parse_commit(rev2);
 
-	rev1->object.flags |= 1;
-	rev2->object.flags |= 2;
+	rev1->object.flags |= PARENT1;
+	rev2->object.flags |= PARENT2;
 	insert_by_date(rev1, &list);
 	insert_by_date(rev2, &list);
 
 	while (interesting(list)) {
 		struct commit *commit = list->item;
 		struct commit_list *parents;
-		int flags = commit->object.flags & 7;
+		int flags = commit->object.flags
+			& (PARENT1 | PARENT2 | UNINTERESTING);
 
 		tmp = list;
 		list = list->next;
 		free(tmp);
-		if (flags == 3) {
+		if (flags == (PARENT1 | PARENT2)) {
 			insert_by_date(commit, &result);
 
 			/* Mark parents of a found merge uninteresting */
@@ -213,21 +210,52 @@ static int merge_base(struct commit *rev1, struct commit *rev2)
 	}
 
 	if (!result)
-		return 1;
+		return NULL;
 
 	if (result->next && list)
 		mark_reachable_commits(result, list);
 
+	/* cull duplicates */
+	for (tmp = result, list = NULL; tmp; ) {
+		struct commit *commit = tmp->item;
+		struct commit_list *next = tmp->next;
+		if (commit->object.flags & UNINTERESTING) {
+			if (list != NULL)
+				list->next = next;
+			free(tmp);
+		} else {
+			if (list == NULL)
+				result = tmp;
+			list = tmp;
+			commit->object.flags |= UNINTERESTING;
+		}
+
+		tmp = next;
+	}
+
+	/* reset flags */
+	clear_commit_marks(rev1, PARENT1 | PARENT2 | UNINTERESTING);
+	clear_commit_marks(rev2, PARENT1 | PARENT2 | UNINTERESTING);
+
+	return result;
+}
+
+static int show_all = 0;
+
+static int merge_base(struct commit *rev1, struct commit *rev2)
+{
+	struct commit_list *result = get_merge_bases(rev1, rev2);
+
+	if (!result)
+		return 1;
+
 	while (result) {
-		struct commit *commit = result->item;
-		result = result->next;
-		if (commit->object.flags & UNINTERESTING)
-			continue;
-		printf("%s\n", sha1_to_hex(commit->object.sha1));
+		printf("%s\n", sha1_to_hex(result->item->object.sha1));
 		if (!show_all)
 			return 0;
-		commit->object.flags |= UNINTERESTING;
+		result = result->next;
 	}
+
 	return 0;
 }