code: function isOption (arg) {
    return (re.short.test(arg) || re.long.test(arg)) && !re.optEquals.test(arg)
  }
docs: Returns true if the supplied arg is in either long (`--one`) or short (`-o`) format.
  @param {string} - the arg to test, e.g. `--one`
  @returns {boolean}
  @static