diff --git a/commit.c b/commit.c
index fe1fa3dc41..9a785bf906 100644
--- a/commit.c
+++ b/commit.c
@@ -544,6 +544,17 @@ struct commit_list *commit_list_insert(struct commit *item, struct commit_list *
 	return new_list;
 }
 
+int commit_list_contains(struct commit *item, struct commit_list *list)
+{
+	while (list) {
+		if (list->item == item)
+			return 1;
+		list = list->next;
+	}
+
+	return 0;
+}
+
 unsigned commit_list_count(const struct commit_list *l)
 {
 	unsigned c = 0;
diff --git a/commit.h b/commit.h
index 5467786c7b..742a6de460 100644
--- a/commit.h
+++ b/commit.h
@@ -167,6 +167,8 @@ int find_commit_subject(const char *commit_buffer, const char **subject);
 
 struct commit_list *commit_list_insert(struct commit *item,
 					struct commit_list **list);
+int commit_list_contains(struct commit *item,
+			 struct commit_list *list);
 struct commit_list **commit_list_append(struct commit *commit,
 					struct commit_list **next);
 unsigned commit_list_count(const struct commit_list *l);