anchor.diff:  const argDebugMode = 'debug';
   const argLaunchBrowser = 'launch-browser';
   const argMachine = 'machine';
  +const argHost = 'host';
   const argPort = 'port';
   const argProfileMemory = 'profile-memory';
   const argTryPorts = 'try-ports';
  
positive.code:   final numPortsToTry =
        args[argTryPorts] != null ? int.tryParse(args[argTryPorts]) ?? 1 : 1;
    final bool verboseMode = args[argVerbose];
  
    // Support collecting profile data.
    final String vmUri = args[argVmUri];
  
negative.code:     negatable: false,
      abbr: 'h',
      help: 'Prints help output.',
    )
    ..addOption(
      argHost,
      defaultsTo: 'localhost',
      help: 'Hostname to serve DevTools on.',
    )
    ..addOption(
      argPort,
  