graph: plug leak

src/graph.c

@@ -22,9 +22,9 @@ static int ahead_behind(git_commit_list_node *one, git_commit_list_node *two,
 	if (git_pqueue_init(&pq, 2, git_commit_list_time_cmp) < 0)
 		return -1;
 	if (git_pqueue_insert(&pq, one) < 0)
-		return -1;
+		goto on_error;
 	if (git_pqueue_insert(&pq, two) < 0)
-		return -1;
+		goto on_error;
 
 	while ((commit = git_pqueue_pop(&pq)) != NULL) {
 		if (commit->flags & RESULT ||
@@ -43,7 +43,12 @@ static int ahead_behind(git_commit_list_node *one, git_commit_list_node *two,
 		commit->flags |= RESULT;
 	}
 
+	git_pqueue_free(&pq);
 	return 0;
+
+on_error:
+	git_pqueue_free(&pq);
+	return -1;
 }
 
 int git_graph_ahead_behind(size_t *ahead, size_t *behind, git_repository *repo,