Move pub into sdk/lib/_internal.

utils/pub/command_help.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 command_help;
-
-import 'dart:async';
-import 'dart:io' as io;
-import 'exit_codes.dart' as exit_codes;
-import 'io.dart';
-import 'log.dart' as log;
-import 'pub.dart';
-
-/// Handles the `help` pub command. 
-class HelpCommand extends PubCommand {
-  String get description => "Display help information for Pub.";
-  String get usage => 'pub help [command]';
-  bool get requiresEntrypoint => false;
-
-  Future onRun() {
-    if (commandOptions.rest.isEmpty) {
-      printUsage();
-    } else {
-      var name = commandOptions.rest[0];
-      var command = pubCommands[name];
-      if (command == null) {
-        log.error('Could not find a command named "$name".');
-        log.error('Run "pub help" to see available commands.');
-        io.exit(exit_codes.USAGE);
-      }
-
-      command.printUsage();
-    }
-  }
-}