private static boolean sameBeforeRevision(@NotNull Change change1, @NotNull Change change2) {
      final ContentRevision b1 = change1.getBeforeRevision();
      final ContentRevision b2 = change2.getBeforeRevision();
      if (b1 != null && b2 != null) {
        final VcsRevisionNumber rn1 = b1.getRevisionNumber();
        final VcsRevisionNumber rn2 = b2.getRevisionNumber();
        return rn1 != VcsRevisionNumber.NULL && rn2 != VcsRevisionNumber.NULL &&
               b1.getClass() == b2.getClass() && rn1.compareTo(rn2) == 0;
      }
      return b1 == null && b2 == null;
    }
private static boolean sameBeforeRevision(@NotNull Change change1, @NotNull Change change2)