@Override
  public FileTimestamp getPreviousStamp(File file, BuildTarget<?> target) throws IOException {
    final TimestampPerTarget[] state = getState(file);
    if (state != null) {
      int targetId = myTargetsState.getBuildTargetId(target);
      for (TimestampPerTarget timestampPerTarget : state) {
        if (timestampPerTarget.targetId == targetId) {
          return FileTimestamp.fromLong(timestampPerTarget.timestamp);
        }
      }
    }
    return FileTimestamp.MINUS_ONE;
  }
@Override
  public FileTimestamp getPreviousStamp(File file, BuildTarget<?> target)