anchor.diff:        });
         callbacks.applyChangesToContext(oldInfo.folder, changeSet);
       }
  +    // TODO(paulberry): every context that was previously a child of oldInfo is
  +    // is still a child of oldInfo.  This is wrong--some of them ought to be
  +    // adopted by newInfo now.
     }
   
     void _handleWatchEvent(Folder folder, ContextInfo info, WatchEvent event) {
  
positive.code:       // are no subfolders that need to be added.
      }
  
      File packageSpec;
  
      if (ENABLE_PACKAGESPEC_SUPPORT) {
        // Start by looking for .packages.
        packageSpec = folder.getChild(PACKAGE_SPEC_NAME);
      }
  
      // Fall back to looking for a pubspec.
      if (packageSpec == null || !packageSpec.exists) {
        packageSpec = folder.getChild(PUBSPEC_NAME);
      }
  
      if (packageSpec.exists) {
        return <ContextInfo>[
          _createContextWithSources(folder, packageSpec, children)
        ];
      }
      // No packagespec? Done.
      if (withPackageSpecOnly) {
        return children;
      }
      // OK, create a context without a packagespec.
      return <ContextInfo>[
        _createContextWithSources(folder, packageSpec, children)
      ];
    }
  
    /**
     * Create a new context associated with the given [folder]. The [pubspecFile]
     * is the `pubspec.yaml` file contained in the folder. Add any sources that
     * are not included in one of the [children] to the context.
     */
    ContextInfo _createContextWithSources(
        Folder folder, File pubspecFile, List<ContextInfo> children) {
      ContextInfo info = _createContext(folder, pubspecFile, children);
      ChangeSet changeSet = new ChangeSet();
      _addSourceFiles(changeSet, folder, info);
      callbacks.applyChangesToContext(folder, changeSet);
      return info;
    }
  
    /**
  
negative.code:    */
    void _extractContext(ContextInfo oldInfo, File packagespecFile) {
      Folder newFolder = packagespecFile.parent;
      ContextInfo newInfo = _createContext(oldInfo, newFolder, packagespecFile);
      // prepare sources to extract
      Map<String, Source> extractedSources = new HashMap<String, Source>();
      oldInfo.sources.forEach((path, source) {
  