Use YAML as the format for the pubspec file.

utils/pub/pub.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.
 
 /**
  * The main entrypoint for the pub command line application.
  */
 #library('pub');
 
+#import('../yaml/yaml.dart');
+
 #import('io.dart');
 #import('utils.dart');
 
 #source('cache.dart');
 #source('command_list.dart');
 #source('command_update.dart');
 #source('package.dart');
 
 Map<String, PubCommand> commands;
 PackageCache cache;
@@ skipping 99 matching lines @@
   final CommandFunction function;
 
   PubCommand(this.description, this.function);
 }
 
 class PubOptions {
   final String cacheDir;
 
   PubOptions(this.cacheDir);
 }