anchor.diff:  import 'package:vm/target/vm.dart' show VmTarget;
   
   void main(List<String> args) async {
  -  var prefix = args.isEmpty ? 'pkg/compiler/' : args.first;
  +  final argParser = ArgParser();
  +  argParser.addFlag('sort-blocking', abbr: 'b');
  +  argParser.addFlag('include-migrated', abbr: 'i');
  +  final argResults = argParser.parse(args);
  +  final sortByBlocking = argResults['sort-blocking'];
  +  final includeMigrated = argResults['include-migrated'];
  +
  +  var prefix =
  +      argResults.rest.isEmpty ? 'pkg/compiler/' : argResults.rest.first;
     var files = <Uri, List<int>>{};
     var isLegacy = <Uri>{};
     var isNullSafe = <Uri>{};
  
positive.code: 
  /// Script to identify good opportunities for null safety migration.
  ///
  /// This script sorts libraries based on a "migratable" order. We compute
  /// this order by counting how many of a library's dependencies have been
  /// migrated.
  
  import 'dart:io';
  
  
negative.code:   final int migratedDependencies;
  
    double get ratio => migratedDependencies / totalDependencies;
  
    FileData(this.isNullSafe, this.totalDependencies, this.migratedDependencies);
  }
  
  