Roll Observatory packages and add a roll script

packages/args/lib/src/help_command.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library args.help_command;
 
 import '../command_runner.dart';
 
 /// The built-in help command that's added to every [CommandRunner].
 ///
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       }
 
       command = commands[name];
       commands = command.subcommands;
       commandString += " $name";
     }
 
     command.printUsage();
   }
 }