anchor.diff:  const String kY = 'y';
   const String kZ = 'z';
   const String kCommit = 'commit';
  +const String kOrigin = 'origin';
  +const String kYes = 'yes';
   const String kHelp = 'help';
   
   const String kUpstreamRemote = 'git@github.com:flutter/flutter.git';
  
positive.code: 
    // PROMPT
  
    print('Your tree is ready to publish Flutter $version (${hash.substring(0, 10)}) '
      'to the "dev" channel.');
    stdout.write('Are you? [yes/no] ');
    if (stdin.readLineSync() != 'yes') {
      runGit('tag -d v$version', 'remove the tag you did not want to publish');
      print('The dev roll has been aborted.');
      exit(0);
    }
  
    runGit('push upstream v$version', 'publish the version');
    runGit('push upstream HEAD:dev', 'land the new version on the "dev" branch');
    print('Flutter version $version has been rolled to the "dev" channel!');
  }
  
  
negative.code:     exit(0);
    }
  
    if (getGitOutput('remote get-url $origin', 'check whether this is a flutter checkout') != kUpstreamRemote) {
      print('The current directory is not a Flutter repository checkout with a correctly configured upstream remote.');
      print('For more details see: https://github.com/flutter/flutter/wiki/Release-process');
      exit(1);
  