anchor.diff:    /**
      * Expands a directory [treeSha] recursively.
      */
  -  Future<List<DiffEntry>> _expandDiffEntry(
  +  static Future<List<DiffEntry>> _expandDiffEntry(
         ObjectStore store, String treeSha, String type) {
   
       List<DiffEntry> diffEntries = [];
  
positive.code:     return treeDiff;
    }
  
  
    /**
     * Diffs given tree objects [oldTree], [newTree] recursively and returns
     * the diff files as [TreeDiffResult].
     */
    Future<TreeDiffResult> diffTreeRecursive(
        ObjectStore store, TreeObject oldTree, TreeObject newTree) {
  
      TreeDiffResult diff = diffTree(oldTree, newTree);
  
negative.code: }
  
  class DiffEntry {
    final TreeEntry oldEntry;
    final TreeEntry newEntry;
    final String type;
    String path;
  
    // String representation of the diff between the two versions of file.
    String diff;
    DiffEntry(this.oldEntry, this.newEntry, this.type,  [String path]) {
      if (path == null) {
        path = oldEntry == null ? newEntry.name : oldEntry.name;
  