adds file path source to pub

utils/pub/system_cache.dart

Index: utils/pub/system_cache.dart
diff --git a/utils/pub/system_cache.dart b/utils/pub/system_cache.dart
index 3074a741188331a2820426075f408ba38846b653..c5264ee6983446f77cc47fa53997a71fd6cb811e 100644
--- a/utils/pub/system_cache.dart
+++ b/utils/pub/system_cache.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -9,6 +9,7 @@ import 'dart:async';
 
 import 'git_source.dart';
 import 'hosted_source.dart';
+import 'path_source.dart';
 import 'io.dart';
 import 'io.dart' as io show createTempDir;
 import 'log.dart' as log;
@@ -48,6 +49,7 @@ class SystemCache {
     cache.register(new SdkSource(sdkDir));
     cache.register(new GitSource());
     cache.register(new HostedSource());
+    cache.register(new PathSource());
     cache.sources.setDefault('hosted');
     return cache;
   }