Add a "help" command to Pub.

utils/tests/pub/pub_test.dart

 // Copyright (c) 2012, 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('pub_tests');
 
 #import('dart:io');
 
 #import('test_pub.dart');
 #import('../../../lib/unittest/unittest.dart');
 
 final USAGE_STRING = """
     Pub is a package manager for Dart.
 
     Usage: pub command [arguments]
 
     Global options:
     -h, --help          Prints this usage information
         --version       Prints the version of Pub
         --[no-]trace    Prints a stack trace when an error occurs
 
     The commands are:
+      help      display help information for Pub
       install   install the current package's dependencies
       list      print the contents of repositories
       update    update the current package's dependencies to the latest versions
       version   print Pub version
 
     Use "pub help [command]" for more information about a command.
     """;
 
 final VERSION_STRING = '''
     Pub 0.0.0
@@ skipping 547 matching lines @@
     ]).scheduleValidate();
 
     run();
   });
 }
 
 versionCommand() {
   test('displays the current version', () =>
     runPub(args: ['version'], output: VERSION_STRING));
 }