@SuppressWarnings("unchecked")
  @Override
  public CommitId get(int index) {
    if (myParents instanceof Object[] array) {
      if (index < 0 || index >= array.length) {
        throw new ArrayIndexOutOfBoundsException(index);
      }
      return (CommitId)array[index];
    }
    if (index != 0) {
      throw new ArrayIndexOutOfBoundsException(index);
    }
    return (CommitId)myParents;
  }
@SuppressWarnings("unchecked")
  @Override
  public CommitId get(int index)