Support Git in pub global activate.

sdk/lib/_internal/pub/test/global/activate/git_package_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.
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
-  integration('runs a script in a path package', () {
-    d.dir("foo", [
+  integration('activates a package from a Git repo', () {
+    ensureGit();
+
+    d.git('foo.git', [
       d.libPubspec("foo", "1.0.0"),
       d.dir("bin", [
         d.file("foo.dart", "main() => print('ok');")
       ])
     ]).create();
 
-    schedulePub(args: ["global", "activate", "--source", "path", "../foo"]);
-
-    var pub = pubRun(global: true, args: ["foo"]);
-    pub.stdout.expect("ok");
-    pub.shouldExit();
+    schedulePub(args: ["global", "activate", "-sgit", "../foo.git"],
+        output: '''
+Resolving dependencies...
+Activated foo 1.0.0 from Git repository "../foo.git".''');
   });
 }