Use "package:" imports for pub.

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.
 
 library pub_tests;
 
 import 'package:path/path.dart' as p;
+import 'package:pub/src/io.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../../../lib/src/io.dart';
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   // Regression test for issue 20947.
   integration('checks out an unfetched and locked revision of a cached '
       'repository', () {
     ensureGit();
 
@@ skipping 39 matching lines @@
       ])
     ]).validate();
 
     d.dir(packagesPath, [
       d.dir('foo', [
         d.file('foo.dart', 'main() => "foo 2";')
       ])
     ]).validate();
   });
 }