anchor.diff:    }
   }
   
  +/**
  + * A set of packages.
  + */
   class PackagesInfo {
     final List<PackageInfo> packages;
   
  
positive.code: 
  Logger _logger = new Logger('pub');
  
  class Pub {
    Directory _cacheDir;
  
  
negative.code:   String toString() => '${packages}';
  }
  
  /**
   * A packake name and version tuple.
   */
  class PackageInfo {
    final String name;
    final String version;
  