Add a "global activate" command to pub.

sdk/lib/_internal/pub/test/global/activate/missing_package_arg_test.dart

Index: sdk/lib/_internal/pub/test/global/activate/missing_package_arg_test.dart
diff --git a/sdk/lib/_internal/pub/test/cache/add/missing_package_arg_test.dart b/sdk/lib/_internal/pub/test/global/activate/missing_package_arg_test.dart
similarity index 55%
copy from sdk/lib/_internal/pub/test/cache/add/missing_package_arg_test.dart
copy to sdk/lib/_internal/pub/test/global/activate/missing_package_arg_test.dart
index e95ede750b4243b4841bbe66d6a6bb8cf302a0fe..c1f3dc121ccfa6de02148efbf5b088e5c9f1a35b 100644
--- a/sdk/lib/_internal/pub/test/cache/add/missing_package_arg_test.dart
+++ b/sdk/lib/_internal/pub/test/global/activate/missing_package_arg_test.dart
@@ -2,22 +2,18 @@
 // 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 '../../../lib/src/exit_codes.dart' as exit_codes;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('fails if no package was given', () {
-    schedulePub(args: ["cache", "add"],
+    schedulePub(args: ["global", "activate"],
         error: """
-            No package to add given.
-            
-            Usage: pub cache add <package> [--version <constraint>] [--all]
-            -h, --help       Print usage information for this command.
-                --all        Install all matching versions.
-            -v, --version    Version constraint.
+            No package to activate given.
+
+            Usage: pub global activate <package> [version]
+            -h, --help    Print usage information for this command.
             """,
         exitCode: exit_codes.USAGE);
   });