anchor.diff:  
   import 'package:chrome/chrome_app.dart' as chrome;
   
  -import 'merge.dart';
  +import 'diff.dart';
   import '../constants.dart';
   import '../exception.dart';
   import '../file_operations.dart';
  
positive.code: 
    static Future smartCheckout(chrome.DirectoryEntry dir, ObjectStore store,
        TreeObject oldTree, TreeObject newTree) {
      TreeDiffResult diff = Merge.diffTree(oldTree, newTree);
      return Future.forEach(diff.adds, (TreeEntry entry) {
        if (entry.isBlob) {
          return ObjectUtils.expandBlob(dir, store, entry.name, entry.sha);
        } else {
  
negative.code:         });
        }
      }).then((_) {
        return Future.forEach(diff.getRemovedEntries(), (DiffEntry diffEntry) {
          return _removeEntryRecursively(store, dir, diffEntry.oldEntry);
        }).then((_) {
          return Future.forEach(diff.getModifiedEntries(), (DiffEntry diffEntry) {
            TreeEntry oldEntry = diffEntry.oldEntry;
            TreeEntry newEntry = diffEntry.newEntry;
            if (newEntry.isBlob) {
              return ObjectUtils.expandBlob(dir, store, newEntry.name,
                  newEntry.sha);
  