anchor.diff:          return folder.isOrContains(includedFolder.path);
         });
         if (!wasIncluded) {
  -        _createContexts(_ancestorInfo, includedFolder, false);
  +        _createContexts(_rootInfo, includedFolder, false);
         }
       }
       // remove newly excluded sources
  
positive.code:    * Create the virtual [ContextInfo] which acts as an ancestor to all other
     * [ContextInfo]s.
     */
    ContextInfo._ancestor()
        : 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 [path] is excluded, as it is in one of the children.
  
negative.code:    * Virtual [ContextInfo] which acts as the ancestor of all other
     * [ContextInfo]s.
     */
    final ContextInfo _rootInfo = new ContextInfo._root();
  
    ContextManagerImpl(this.resourceProvider, this.packageResolverProvider,
        this._packageMapProvider, this._instrumentationService) {
  