private void addUnderdoneEdge(int upNodeIndex, CommitId downCommitId) {
    List<Integer> upNodes = upAdjacentNodes.get(downCommitId);
    if (upNodes == null) {
      upNodes = new SmartList<>();
      upAdjacentNodes.put(downCommitId, upNodes);
    }
    upNodes.add(upNodeIndex);
  }
private void addUnderdoneEdge(int upNodeIndex, CommitId downCommitId)