Rationalize arg handling for pub build and serve.

sdk/lib/_internal/pub/test/barback/directory_args_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 'package:scheduled_test/scheduled_test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import '../serve/utils.dart';
+
+main() {
+  initConfig();
+
+  setUp(() {
+    d.dir(appPath, [
+      d.appPubspec(),
+      d.dir('asset', [d.file('file.txt', 'asset')]),
+      d.dir('bar', [d.file('file.txt', 'bar')]),
+      d.dir('foo', [d.file('file.txt', 'foo')]),
+      d.dir('test', [d.file('file.txt', 'test')]),
+      d.dir('web', [d.file('file.txt', 'web')])
+    ]).create();
+  });
+
+  integration("builds only the given directories", () {
+    schedulePub(args: ["build", "foo", "bar"],
+        output: new RegExp(r'Built 4 files to "build".'));
+
+    d.dir(appPath, [
+      d.dir('build', [
+        d.dir('bar', [
+          d.file('file.txt', 'bar'),
+          d.dir('assets', [
+            d.dir('myapp', [
+              d.file('file.txt', 'asset')
+            ])
+          ])
+        ]),
+        d.dir('foo', [
+          d.file('file.txt', 'foo'),
+          d.dir('assets', [
+            d.dir('myapp', [
+              d.file('file.txt', 'asset')
+            ])
+          ])
+        ]),
+        d.nothing('test'),
+        d.nothing('web')
+      ])
+    ]).validate();
+  });
+
+  integration("serves only the given directories", () {
+    pubServe(args: ["foo", "bar"]);
+
+    requestShouldSucceed("file.txt", "bar", root: "bar");
+    requestShouldSucceed("file.txt", "foo", root: "foo");
+    expectNotServed("test");
+    expectNotServed("web");
+
+    endPubServe();
+  });
+}