_append(filepath, data) {
    data = data || {};
    let task = {
      source: null,
      filepath: filepath,
    };
    if (!data.name) {
      data.name = filepath;
    }
    data.sourcePath = filepath;
    task.data = data;
    this._entriesCount++;
    if (data.stats && data.stats instanceof Stats) {
      task = this._updateQueueTaskWithStats(task, data.stats);
      if (task) {
        if (data.stats.size) {
          this._fsEntriesTotalBytes += data.stats.size;
        }
        this._queue.push(task);
      }
    } else {
      this._statQueue.push(task);
    }
  }
Internal helper for appending files.

@private
@param  {String} filepath The source filepath.
@param  {EntryData} data The entry data.
@return void