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

test/get/git/check_out_unfetched_revision_of_cached_repo_test.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.
 
 import 'package:path/path.dart' as p;
 import 'package:pub/src/io.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
@@ skipping 29 matching lines @@
     pubUpgrade(output: contains("Changed 1 dependency!"));
 
     // Switch back to the old cache.
     schedule(() {
       var cacheDir = p.join(sandboxDir, cachePath);
       deleteEntry(cacheDir);
       renameDir(p.join(sandboxDir, "$cachePath.old"), cacheDir);
     });
 
     // Get the updated version of the git dependency based on the lockfile.
-    pubGet();
+    // TODO(rnystrom): Remove "--packages-dir" and validate using the
+    // ".packages" file instead of looking in the "packages" directory.
+    pubGet(args: ["--packages-dir"]);
 
     d.dir(cachePath, [
       d.dir('git', [
         d.dir('cache', [d.gitPackageRepoCacheDir('foo')]),
         d.gitPackageRevisionCacheDir('foo'),
         d.gitPackageRevisionCacheDir('foo', 2)
       ])
     ]).validate();
 
     d.dir(packagesPath, [
       d.dir('foo', [
         d.file('foo.dart', 'main() => "foo 2";')
       ])
     ]).validate();
   });
 }