anchor.diff:    var step = arguments[0];
     var testDir = arguments[1];
   
  +  // If the test directory is just a single identifier, assume it's a language
  +  // test subdirectory.
  +  if (!testDir.contains("/")) testDir = "language_2/$testDir";
  +
     switch (step) {
       case "branch":
         _createBranch(testDir);
  
positive.code:   print(bold("  dart tools/migration/bin/migrate.dart "
        "${dryRun ? '--dry-run ' : ''}$step $testDir"));
  }
  
negative.code: 
      case "copy":
        _copyFiles(testDir);
        break;
  
      case "fork":
        _forkFiles(testDir);
        break;
  
      case "analyze":
  