Make "--no-packages-dir" the default.

test/dev_dependency_test.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.
 
 import 'descriptor.dart' as d;
 import 'test_pub.dart';
 
 main() {
   integration("includes root package's dev dependencies", () {
     d.dir('foo', [
@@ skipping 11 matching lines @@
         "name": "myapp",
         "dev_dependencies": {
           "foo": {"path": "../foo"},
           "bar": {"path": "../bar"},
         }
       })
     ]).create();
 
     pubGet();
 
-    d.dir(packagesPath, [
-      d.dir("foo", [
-        d.file("foo.dart", 'main() => "foo";')
-      ]),
-      d.dir("bar", [
-        d.file("bar.dart", 'main() => "bar";')
-      ])
-    ]).validate();
+    d.appPackagesFile({
+      "foo": "../foo",
+      "bar": "../bar"
+    }).validate();
   });
 
   integration("includes dev dependency's transitive dependencies", () {
     d.dir('foo', [
       d.libDir('foo'),
       d.libPubspec('foo', '0.0.1', deps: {
         "bar": {"path": "../bar"}
       })
     ]).create();
 
     d.dir('bar', [
       d.libDir('bar'),
       d.libPubspec('bar', '0.0.1')
     ]).create();
 
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "dev_dependencies": {
           "foo": {"path": "../foo"}
         }
       })
     ]).create();
 
     pubGet();
 
-    d.dir(packagesPath, [
-      d.dir("foo", [
-        d.file("foo.dart", 'main() => "foo";')
-      ]),
-      d.dir("bar", [
-        d.file("bar.dart", 'main() => "bar";')
-      ])
-    ]).validate();
+    d.appPackagesFile({
+      "foo": "../foo",
+      "bar": "../bar"
+    }).validate();
   });
 
   integration("ignores transitive dependency's dev dependencies", () {
     d.dir('foo', [
       d.libDir('foo'),
       d.pubspec({
         "name": "foo",
         "version": "0.0.1",
         "dev_dependencies": {
           "bar": {"path": "../bar"}
         }
       })
     ]).create();
 
     d.dir('bar', [
       d.libDir('bar'),
       d.libPubspec('bar', '0.0.1')
     ]).create();
 
     d.dir(appPath, [
       d.appPubspec({
         "foo": {"path": "../foo"}
       })
     ]).create();
 
     pubGet();
 
-    d.dir(packagesPath, [
-      d.dir("foo", [
-        d.file("foo.dart", 'main() => "foo";')
-      ]),
-      d.nothing("bar")
-    ]).validate();
+    d.appPackagesFile({
+      "foo": "../foo"
+    }).validate();
   });
 }