Support pub --with-prejudice.

sdk/lib/_internal/pub/lib/src/command.dart

 // Copyright (c) 2013, 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.command;
 
 import 'dart:async';
 import 'dart:math' as math;
 
 import 'package:args/args.dart';
@@ skipping 277 matching lines @@
       help: 'Control output verbosity.',
       allowed: ['normal', 'io', 'solver', 'all'],
       allowedHelp: {
         'normal': 'Show errors, warnings, and user messages.',
         'io':     'Also show IO operations.',
         'solver': 'Show steps during version resolution.',
         'all':    'Show all output including internal tracing messages.'
       });
   argParser.addFlag('verbose', abbr: 'v', negatable: false,
       help: 'Shortcut for "--verbosity=all".');
+  argParser.addFlag('with-prejudice', hide: !isAprilFools, negatable: false,
+      help: 'Execute commands with prejudice.');
 
   // Register the commands.
   PubCommand.mainCommands.forEach((name, command) {
     _registerCommand(name, command, argParser);
   });
 
   return argParser;
 }
 
 /// Registers a [command] with [name] on [parser].
 void _registerCommand(String name, PubCommand command, ArgParser parser) {
   parser.addCommand(name, command.commandParser);
 
   // Recursively wire up any subcommands.
   command.subcommands.forEach((name, subcommand) {
     _registerCommand(name, subcommand, command.commandParser);
   });
 }