public boolean selectRevisions(int first, int second) {
    int l, r;
    if (first == second) {
      r = -1;
      l = first == -1 ? 0 : first;
    }
    else {
      r = first;
      l = second;
    }
    if (myRightRevisionIndex == r && myLeftRevisionIndex == l) {
      return false;
    }
    myRightRevisionIndex = r;
    myLeftRevisionIndex = l;
    resetEntriesCache();
    return true;
  }
public boolean selectRevisions(int first, int second)