Start pulling pub from its own repo.

sdk/lib/_internal/pub/test/snapshot/updates_snapshot_for_git_dependency_test.dart

-// Copyright (c) 2014, 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:scheduled_test/scheduled_test.dart';
-
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("upgrades a snapshot when a git dependency is upgraded", () {
-    ensureGit();
-
-    d.git('foo.git', [
-      d.pubspec({
-        "name": "foo",
-        "version": "0.0.1"
-      }),
-      d.dir("bin", [
-        d.file("hello.dart", "void main() => print('Hello!');")
-      ])
-    ]).create();
-
-    d.appDir({"foo": {"git": "../foo.git"}}).create();
-
-    pubGet(output: contains("Precompiled foo:hello."));
-
-    d.dir(p.join(appPath, '.pub', 'bin', 'foo'), [
-      d.matcherFile('hello.dart.snapshot', contains('Hello!'))
-    ]).validate();
-
-    d.git('foo.git', [
-      d.dir("bin", [
-        d.file("hello.dart", "void main() => print('Goodbye!');")
-      ])
-    ]).commit();
-
-    pubUpgrade(output: contains("Precompiled foo:hello."));
-
-    d.dir(p.join(appPath, '.pub', 'bin', 'foo'), [
-      d.matcherFile('hello.dart.snapshot', contains('Goodbye!'))
-    ]).validate();
-
-    var process = pubRun(args: ['foo:hello']);
-    process.stdout.expect("Goodbye!");
-    process.shouldExit();
-  });
-}