Don't allow overlapping source directories.

sdk/lib/_internal/pub/test/serve/web_socket/unserve_directory_superdirectory_still_watched_test.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS d.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 '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-import '../utils.dart';
-
-main() {
-  initConfig();
-  integration("when a superdirectory is unbound it is still watched because "
-      "the subdirectory is watching it", () {
-    d.dir(appPath, [
-      d.appPubspec(),
-      d.dir("example", [
-        d.dir("one", [
-          d.file("foo.txt", "before")
-        ])
-      ])
-    ]).create();
-
-    var exampleOne = p.join("example", "one");
-    pubServe(args: [exampleOne, "example"]);
-
-    requestShouldSucceed("one/foo.txt", "before", root: "example");
-    requestShouldSucceed("foo.txt", "before", root: exampleOne);
-
-    // Unbind the subdirectory.
-    expectWebSocketResult("unserveDirectory", {"path": "example"}, {
-      "url": getServerUrl("example")
-    });
-
-    // "example" should not be served now.
-    requestShouldNotConnect("one/foo.txt", root: "example");
-
-    // "example/one" is still fine.
-    requestShouldSucceed("foo.txt", "before", root: exampleOne);
-
-    // And still being watched.
-    d.dir(appPath, [
-      d.appPubspec(),
-      d.dir("example", [
-        d.dir("one", [
-          d.file("foo.txt", "after")
-        ])
-      ])
-    ]).create();
-
-    waitForBuildSuccess();
-    requestShouldSucceed("foo.txt", "after", root: exampleOne);
-
-    endPubServe();
-  });
-}