anchor.diff:  
     /// Validates and stores [value] as the value for [option], which must be a
     /// flag.
  -  void setFlag(Map results, Option option, bool value) {
  +  void _setFlag(Map results, Option option, bool value) {
       assert(option.isFlag);
       results[option.name] = value;
     }
  
positive.code:   /// Called during parsing to validate the arguments.
    ///
    /// Throws an [ArgParserException] if [condition] is `false`.
    void validate(bool condition, String message) {
      if (!condition) throw ArgParserException(message);
    }
  
    /// Validates and stores [value] as the value for [option], which must not be
    /// a flag.
    void setOption(Map results, Option option, String value) {
      assert(!option.isFlag);
  
      if (!option.isMultiple) {
  
negative.code:   /// Tries to parse the current argument as a series of collapsed abbreviations
    /// (like "-abc") or a single abbreviation with the value directly attached
    /// to it (like "-mrelease").
    bool _parseAbbreviation(Parser innermostCommand) {
      // Hand coded regexp: r'^-([a-zA-Z0-9]+)(.*)$'
      // Hyphen then at least one letter/digit then zero or more
      // anything-but-newlines.
      if (_current.length < 2) return false;
      if (!_current.startsWith('-')) return false;
  
      // Find where we go from letters/digits to rest.
      var index = 1;
      while (index < _current.length &&
          _isLetterOrDigit(_current.codeUnitAt(index))) {
        ++index;
      }
      // Must be at least one letter/digit.
  