anchor.diff:  
     /// Return the content of the file with navigation links and anchors added.
     String _computeNavigationContent(UnitInfo unitInfo) {
  +    String unitDir = _directoryContaining(unitInfo);
       String content = unitInfo.content;
       OffsetMapper mapper = unitInfo.offsetMapper;
       Map<int, String> openInsertions = {};
  
positive.code:     return regions;
    }
  
    /// Return the URL that will navigate to the given [target].
    String _uriForTarget(NavigationTarget target) {
      if (target == null) {
        // TODO(brianwilkerson) This is temporary support until we can get targets
        //  for all nodes.
        return '';
      }
      path.Context pathContext = migrationInfo.pathContext;
      String targetPath = pathContext.setExtension(target.filePath, '.html');
      String sourceDir = pathContext.dirname(unitInfo.path);
      String relativePath = pathContext.relative(targetPath, from: sourceDir);
      return '$relativePath#o${target.offset.toString()}';
    }
  }
  
negative.code:   /// * 'explanation': The Mustache context for the tooltip explaining why the
    ///   content in this region was modified.
    List<Map> _computeRegions(UnitInfo unitInfo) {
      String unitDir = _directoryContaining(unitInfo);
      String content = unitInfo.content;
      List<Map> regions = [];
      int previousOffset = 0;
  