anchor.diff:  
       return new Future.value();
     }
  -
  -  //
  -  // - PackageBuilder virtual interface.
  -  //
   
     Future _analyzePubspec(File file) {
       file.clearMarkers(_packageServiceName);
  
positive.code:  * A class to help resolve pub `package:` references.
   */
  class _PubResolver extends PackageResolver {
    final Project project;
  
    _PubResolver._(this.project);
  
    //
    // PackageResolver virtual interface:
    //
  
    PackageServiceProperties get properties => pubProperties;
  
  
negative.code:     return new Future.value();
    }
  
    Future _installUpgradePackages(
        Folder container,
        String commandName,
  