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

test/get/path/shared_dependency_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 d.file.
 
 import 'package:path/path.dart' as path;
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
@@ skipping 19 matching lines @@
 
     d.dir(appPath, [
       d.appPubspec({
         "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";')]),
-      d.dir("shared", [d.file("shared.dart", 'main() => "shared";')])
-    ]).validate();
+    d.appPackagesFile({
+      "foo": "../foo",
+      "bar": "../bar",
+      "shared": "../shared"
+    }).validate();
   });
 
   integration("shared dependency with paths that normalize the same", () {
     d.dir("shared", [
       d.libDir("shared"),
       d.libPubspec("shared", "0.0.1")
     ]).create();
 
     d.dir("foo", [
       d.libDir("foo"),
@@ skipping 11 matching lines @@
 
     d.dir(appPath, [
       d.appPubspec({
         "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";')]),
-      d.dir("shared", [d.file("shared.dart", 'main() => "shared";')])
-    ]).validate();
+    d.appPackagesFile({
+      "foo": "../foo",
+      "bar": "../bar",
+      "shared": "../shared"
+    }).validate();
   });
 
   integration("shared dependency with absolute and relative path", () {
     d.dir("shared", [
       d.libDir("shared"),
       d.libPubspec("shared", "0.0.1")
     ]).create();
 
     d.dir("foo", [
       d.libDir("foo"),
@@ skipping 11 matching lines @@
 
     d.dir(appPath, [
       d.appPubspec({
         "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";')]),
-      d.dir("shared", [d.file("shared.dart", 'main() => "shared";')])
-    ]).validate();
+    d.appPackagesFile({
+      "foo": "../foo",
+      "bar": "../bar",
+      "shared": path.join(sandboxDir, "shared")
+    }).validate();
   });
 }