final synchronized void mergeInit(MergePolicy.OneMerge merge) throws IOException {
    boolean success = false;
    try {
      _mergeInit(merge);
      success = true;
    } finally {
      if (!success) {
        if (infoStream.isEnabled("IW")) {
          infoStream.message("IW", "hit exception in mergeInit");
        }
        mergeFinish(merge);
      }
    }
  }