dateFile misleading parameter daysToKeep #1080

class DateRollingFileStream extends RollingFileWriteStream {
  constructor(filename, pattern, options) {
    //...
    if (options.daysToKeep) {
      options.numToKeep = options.daysToKeep;
    }
}

class RollingFileWriteStream extends Writable {
  //...
  // Sorted from the oldest to the latest
  async _getExistingFiles() {
    const files = await fs.readdir(this.fileObject.dir).catch(() => []);

    debug(`_getExistingFiles: files=${files}`);
    const existingFileDetails = files
      .map(n => this.fileNameParser(n))
      .filter(n => n);

    const getKey = n =>
      (n.timestamp ? n.timestamp : newNow().getTime()) - n.index;
    existingFileDetails.sort((a, b) => getKey(a) - getKey(b));

    return existingFileDetails;
  }
  //...
  async _clean() {
    const existingFileDetails = await this._getExistingFiles();
    debug(
      `_clean: numToKeep = ${this.options.numToKeep}, existingFiles = ${existingFileDetails.length}`
    );
    debug("_clean: existing files are: ", existingFileDetails);
    if (this._tooManyFiles(existingFileDetails.length)) {
      const fileNamesToRemove = existingFileDetails
        .slice(0, existingFileDetails.length - this.options.numToKeep - 1)
        .map(f => path.format({ dir: this.fileObject.dir, base: f.filename }));
      await deleteFiles(fileNamesToRemove);
    }
  }
}