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

test/get/git/locked_revision_without_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 path;
 import 'package:pub/src/io.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 // Regression test for issue 16470.
 
 main() {
   integration('checks out the repository for a locked revision', () {
     ensureGit();
 
     d.git('foo.git', [
       d.libDir('foo'),
       d.libPubspec('foo', '1.0.0')
     ]).create();
 
     d.appDir({"foo": {"git": "../foo.git"}}).create();
 
     // This get should lock the foo.git dependency to the current revision.
-    pubGet();
+    pubGet(args: ["--packages-dir"]);
 
     d.dir(packagesPath, [
       d.dir('foo', [
         d.file('foo.dart', 'main() => "foo";')
       ])
     ]).validate();
 
     // Delete the packages path and the cache to simulate a brand new checkout
     // of the application.
     schedule(() => deleteEntry(path.join(sandboxDir, packagesPath)));
     schedule(() => deleteEntry(path.join(sandboxDir, cachePath)));
 
     d.git('foo.git', [
       d.libDir('foo', 'foo 2'),
       d.libPubspec('foo', '1.0.0')
     ]).commit();
 
     // This get shouldn't upgrade the foo.git dependency due to the lockfile.
-    pubGet();
+    pubGet(args: ["--packages-dir"]);
 
     d.dir(packagesPath, [
       d.dir('foo', [
         d.file('foo.dart', 'main() => "foo";')
       ])
     ]).validate();
   });
 }