anchor.diff:    await new File(p.join(repository, dartRbFileName)).writeAsString(
         createDartFormula(revisions, hashes, devVersion, stableVersion),
         flush: true);
  +  await new File(p.join(repository, dart2RbFileName)).writeAsString(
  +      createDart2Formula(revisions, hashes, devVersion, stableVersion),
  +      flush: true);
   }
   
   String createDartFormula(
  
positive.code: const contentShellFile = 'dartium/content_shell-macos-x64-release.zip';
  
  const dartRbFileName = 'dart.rb';
  
  Future<String> getHash256(
      String channel, String revision, String download) async {
  
negative.code: end
  ''';
  
  /// TODO: Remove this formula after Dart 2 is released as stable.
  /// This is a transitional mechanism to support developers migrating
  /// from Dart 1 to Dart 2 while it's in pre-release.
  String createDart2Formula(
          Map revisions, Map hashes, String devVersion, String stableVersion) =>
      '''
  class DartAT2 < Formula
    desc "The Dart 2 SDK"
    homepage "https://www.dartlang.org/"
    version "$devVersion"
  
    keg_only :versioned_formula
  
    if MacOS.prefer_64_bit?
      url "$urlBase/dev/release/${revisions['dev']}/$x64File"
      sha256 "${hashes['dev'][x64File]}"
    else
      url "$urlBase/dev/release/${revisions['dev']}/$ia32File"
      sha256 "${hashes['dev'][ia32File]}"
    end
  
    def install
      libexec.install Dir["*"]
      bin.install_symlink "#{libexec}/bin/dart"
      bin.write_exec_script Dir["#{libexec}/bin/{pub,dart?*}"]
    end
  
    def shim_script(target)
      <<~EOS
        #!/usr/bin/env bash
        exec "#{prefix}/#{target}" "$@"
      EOS
    end
  
    def caveats; <<~EOS
      Note that this is a prerelease version of Dart.
  
      Please note the path to the Dart SDK:
        #{opt_libexec}
      EOS
    end
  
    test do
      (testpath/"sample.dart").write <<~EOS
        void main() {
          print(r"test message");
        }
      EOS
  
      assert_equal "test message\n", shell_output("#{bin}/dart sample.dart")
    end
  end
  ''';
  
  
  Future runGit(List<String> args, String repository,
      Map<String, String> gitEnvironment) async {
    print("git ${args.join(' ')}");
  