Add a "cache add" command to download packages to the cache.

sdk/lib/_internal/pub/test/cache/add/all_with_some_versions_present_test.dart

Index: sdk/lib/_internal/pub/test/cache/add/all_with_some_versions_present_test.dart
diff --git a/sdk/lib/_internal/pub/test/cache/add/all_with_some_versions_present_test.dart b/sdk/lib/_internal/pub/test/cache/add/all_with_some_versions_present_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3a900772ea270f7f4b398aa9978aedbcbb55d93c
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/cache/add/all_with_some_versions_present_test.dart
@@ -0,0 +1,40 @@
+// 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 '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+
+main() {
+  initConfig();
+  integration('"--all" adds all non-installed versions of the package', () {
+    servePackages([
+      packageMap("foo", "1.2.1"),
+      packageMap("foo", "1.2.2"),
+      packageMap("foo", "1.2.3"),
+      packageMap("foo", "2.0.0")
+    ]);
+
+    // Install a couple of versions first.
+    schedulePub(args: ["cache", "add", "foo", "-v", "1.2.1"],
+        output: 'Downloading foo 1.2.1...');
+
+    schedulePub(args: ["cache", "add", "foo", "-v", "1.2.3"],
+        output: 'Downloading foo 1.2.3...');
+
+    // They should show up as already installed now.
+    schedulePub(args: ["cache", "add", "foo", "--all"],
+        output: '''
+          Already cached foo 1.2.1.
+          Downloading foo 1.2.2...
+          Already cached foo 1.2.3.
+          Downloading foo 2.0.0...''');
+
+    d.cacheDir({"foo": "1.2.1"}).validate();
+    d.cacheDir({"foo": "1.2.2"}).validate();
+    d.cacheDir({"foo": "1.2.3"}).validate();
+    d.cacheDir({"foo": "2.0.0"}).validate();
+  });
+}