anchor.diff:  class ProjectTemplate {
     String _id;
     String _sourceUri;
  -  List<TemplateVar> _vars = [];
  +  List<_TemplateVar> _vars = [];
   
     ProjectTemplate(this._id,
                     [Map<String, String> globalVars,
  
positive.code:   }
  
    String _interpolateTemplateVars(String text) {
      return _vars.fold(text, (String t, TemplateVar v) => v.interpolate(t));
    }
  
    Future _traverseElement(DirectoryEntry destRoot, DirectoryEntry sourceRoot,
  
negative.code: /**
   * Specifies a variable-to-value substitution in a template file text.
   */
  class _TemplateVar {
    final String name;
    final String value;
  
    _TemplateVar(this.name, this.value);
  
    String interpolate(String text) => text.replaceAll('``$name``', value);
  }
  