code: function isEmpty(files, dir, acc, opts) {
    var filter = opts.filter || isGarbageFile;
    for (const file of files) {
      const fp = path.join(dir, file);
  
      if (opts.dryRun && acc.indexOf(fp) !== -1) {
        continue;
      }
      if (filter(fp) === false) {
        return false;
      }
    }
    return true;
  }
docs: Return true if the given `files` array has zero length or only
  includes unwanted files.