anchor.diff:      }, cancelOnError: cancelOnError);
       _subscriptions.add(subscription);
     }
  -
  -  /// Return a human-friendly string representation of [event].
  -  String _formatEvent(FileSystemEvent event) {
  -    if (event == null) return 'null';
  -
  -    var path = p.relative(event.path, from: directory);
  -    var type = event.isDirectory ? 'directory' : 'file';
  -    if (event is FileSystemCreateEvent) {
  -      return "create $type $path";
  -    } else if (event is FileSystemDeleteEvent) {
  -      return "delete $type $path";
  -    } else if (event is FileSystemModifyEvent) {
  -      return "modify $type $path";
  -    } else if (event is FileSystemMoveEvent) {
  -      return "move $type $path to "
  -          "${p.relative(event.destination, from: directory)}";
  -    }
  -  }
  -
  -  // TODO(nweiz): remove this when the buildbots calm down.
  -  /// Whether this code is running on a buildbot.
  -  bool get _runningOnBuildbot =>
  -    Platform.environment.containsKey('BUILDBOT_BUILDERNAME');
   }
  
positive.code: 
    /// The callback that's run when [Directory.watch] emits a batch of events.
    void _onBatch(List<FileSystemEvent> batch) {
      if (_runningOnBuildbot) {
        print("======== batch:");
        for (var event in batch) {
          print("  ${_formatEvent(event)}");
        }
  
        print("known files:");
        for (var foo in _files.toSet()) {
          print("  ${p.relative(foo, from: directory)}");
        }
      }
  
      batches++;
  
      _sortEvents(batch).forEach((path, events) {
        var relativePath = p.relative(path, from: directory);
        if (_runningOnBuildbot) {
          print("events for $relativePath:\n");
          for (var event in events) {
            print("  ${_formatEvent(event)}");
          }
        }
  
        var canonicalEvent = _canonicalEvent(events);
        events = canonicalEvent == null ?
            _eventsBasedOnFileSystem(path) : [canonicalEvent];
        if (_runningOnBuildbot) {
          print("canonical event for $relativePath: "
              "${_formatEvent(canonicalEvent)}");
          print("actionable events for $relativePath: "
              "${events.map(_formatEvent)}");
        }
  
        for (var event in events) {
          if (event is FileSystemCreateEvent) {
  
negative.code: 
  import 'dart:async';
  import 'dart:io';
  
  import '../constructable_file_system_event.dart';
  import '../path_set.dart';
  