anchor.diff:  /// If [library] is specified, we set the packageName field. If no package could
   /// be determined, we return an empty string.
   String _findPackage(LibraryMirror mirror, [Library library]) {
  +  if (library == null) {
  +    library = entityMap[mirror.simpleName];
  +  }
  +  if (library != null) {
  +    if (library.hasBeenCheckedForPackage) return library.packageName;
  +    library.hasBeenCheckedForPackage = true;
  +  }
     if (mirror.uri.scheme != 'file') return '';
     var filePath = mirror.uri.toFilePath();
     // We assume that we are documenting only libraries under package/lib
  
positive.code:     inlineSyntaxes: markdownSyntaxes);
    return contents;
  }
  
  
  List<String> _listLibraries(List<String> args) {
    var libraries = new List<String>();
  
negative.code:   ClassGroup classes;
  
    String packageName = '';
    bool hasBeenCheckedForPackage = false;
  
    String get packagePrefix => packageName == null || packageName.isEmpty
        ? ''
  