@Override
  public Comparator<TreeNodeOnVcsRevision> getComparator() {
    final Comparator<VcsFileRevision> comparator = myBaseColumn.getComparator();
    if (comparator == null) return null;
    return (o1, o2) -> {
      if (o1 == null) return -1;
      if (o2 == null) return 1;
      VcsFileRevision revision1 = o1.getRevision();
      VcsFileRevision revision2 = o2.getRevision();
      return comparator.compare(revision1, revision2);
    };
  }
@Override
  public Comparator<TreeNodeOnVcsRevision> getComparator()