docs: function fileSystem(context, settings, next) {
    var input = context.files
  
    if (input.length === 0) {
      next()
    } else {
      find(
        input,
        {
          cwd: settings.cwd,
          extensions: settings.extensions,
          silentlyIgnore: settings.silentlyIgnore,
          ignore: new Ignore({
            cwd: settings.cwd,
            detectIgnore: settings.detectIgnore,
            ignoreName: settings.ignoreName,
            ignorePath: settings.ignorePath
          })
        },
        onfound
      )
    }
  
    function onfound(error, result) {
      var output = result.files
  
      /* Sort alphabetically. Everything’s unique so we don’t care
       * about cases where left and right are equal. */
      output.sort(sortAlphabetically)
  
      /* Mark as given.  This allows outputting files,
       * which can be pretty dangerous, so it’s “hidden”. */
      output.forEach(markAsGiven)
  
      context.files = output
  
      /* If `out` wasn’t set, detect it based on
       * whether one file was given. */
      if (settings.out === null || settings.out === undefined) {
        settings.out = result.oneFileMode
      }
  
      next(error)
    }
  
    function markAsGiven(file) {
      file.data.unifiedEngineGiven = true
    }
  
    function sortAlphabetically(left, right) {
      return left.path < right.path ? -1 : 1
    }
  }