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

test/test_pub.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.
 
 /// Test infrastructure for testing pub.
 ///
 /// Unlike typical unit tests, most pub tests are integration tests that stage
 /// some stuff on the file system, run pub, and then validate the results. This
 /// library provides an API to build tests like that.
 import 'dart:async';
@@ skipping 57 matching lines @@
 final String cachePath = "cache";
 
 /// The path of the mock app directory used for tests, relative to the sandbox
 /// directory.
 final String appPath = "myapp";
 
 /// The path of the packages directory in the mock app used for tests, relative
 /// to the sandbox directory.
 final String packagesPath = "$appPath/packages";
 
+/// The path of the ".packages" file in the mock app used for tests, relative
+/// to the sandbox directory.
+final String packagesFilePath = "$appPath/.packages";
+
 /// Set to true when the current batch of scheduled events should be aborted.
 bool _abortScheduled = false;
 
 /// Enum identifying a pub command that can be run with a well-defined success
 /// output.
 class RunCommand {
   static final get = new RunCommand('get', new RegExp(
       r'Got dependencies!|Changed \d+ dependenc(y|ies)!'));
   static final upgrade = new RunCommand('upgrade', new RegExp(
       r'(No dependencies changed\.|Changed \d+ dependenc(y|ies)!)$'));
@@ skipping 679 matching lines @@
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     return description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }
 
 /// A [StreamMatcher] that matches multiple lines of output.
 StreamMatcher emitsLines(String output) => inOrder(output.split("\n"));