Add a --[no]-packages-dir flag.

lib/src/command_runner.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.
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:http/http.dart' as http;
@@ skipping 42 matching lines @@
           '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.');
     argParser.addFlag('sparkle', hide: !isAprilFools,
         negatable: false, help: 'A more sparkly experience.');
-    argParser.addFlag('package-symlinks',
-        negatable: true, defaultsTo: true, hide: true,
-        help: "Generate packages/ directories when installing packages.");
 
     addCommand(new BuildCommand());
     addCommand(new CacheCommand());
     addCommand(new DepsCommand());
     addCommand(new DowngradeCommand());
     addCommand(new GlobalCommand());
     addCommand(new GetCommand());
     addCommand(new ListPackageDirsCommand());
     addCommand(new LishCommand());
     addCommand(new RunCommand());
@@ skipping 140 matching lines @@
   Future _validatePlatform() async {
     if (Platform.operatingSystem != 'windows') return;
 
     var result = await runProcess('ver', []);
     if (result.stdout.join('\n').contains('XP')) {
       log.error('Sorry, but pub is not supported on Windows XP.');
       await flushThenExit(exit_codes.USAGE);
     }
   }
 }