Start pulling pub from its own repo.

sdk/lib/_internal/pub/test/get/git/require_pubspec_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 '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('requires the dependency to have a pubspec', () {
-    ensureGit();
-
-    d.git('foo.git', [
-      d.libDir('foo')
-    ]).create();
-
-    d.appDir({"foo": {"git": "../foo.git"}}).create();
-
-    pubGet(error: new RegExp(r'Could not find a file named "pubspec\.yaml" '
-        r'in "[^\n]*"\.'));
-  });
-}