anchor.diff:     * Create the virtual [ContextInfo] which acts as an ancestor to all other
      * [ContextInfo]s.
      */
  -  ContextInfo._ancestor()
  +  ContextInfo._root()
         : folder = null,
           pathFilter = null;
   
     /**
  -   * Returns `true` if the folder associated with this context is not contained
  -   * within any other folders that have an associated context.
  -   */
  -  bool get isRoot => parent.parent == null;
  +   * Returns `true` if this is a "top level" context, meaning that the folder
  +   * associated with it is not contained within any other folders that have an
  +   * associated context.
  +   */
  +  bool get isTopLevel => parent.parent == null;
   
     /**
      * Returns `true` if [path] is excluded, as it is in one of the children.
  
positive.code:         } else {
            // pubspec was added in a sub-folder, extract a new context
            if (_isPubspec(path) &&
                info.isRoot &&
                !info.isPathToPackageDescription(path)) {
              _extractContext(info, resource);
              return;
  
negative.code:         return folder.isOrContains(includedFolder.path);
        });
        if (!wasIncluded) {
          _createContexts(_rootInfo, includedFolder, false);
        }
      }
      // remove newly excluded sources
  