code: function opt(argv, arg, index, key) {
      var value = argv[index + 1], equals = arg.indexOf('=');
      if(equals > -1) {
        value = arg.substr(equals + 1);
      }
      if(value && ~keys.indexOf(value)) {
        return value;
      }
      if(arg === option[key]) {
        return modes[key];
      }
    }
docs: parse long options