Add isWithin to pkg/path.

pkg/path/test/posix_test.dart

 // Copyright (c) 2012, 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 path.test.posix_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:path/path.dart' as path;
 
 main() {
@@ skipping 393 matching lines @@
       expect(r.relative('..', from: 'foo/bar'), equals('../../..'));
     });
 
     test('from a . root', () {
       var r = new path.Builder(style: path.Style.posix, root: '.');
       expect(r.relative('/foo/bar/baz'), equals('/foo/bar/baz'));
       expect(r.relative('foo/bar/baz'), equals('foo/bar/baz'));
     });
   });
 
+  group('isWithin', () {
+    test('simple cases', () {
+      expect(builder.isWithin('foo/bar', 'foo/bar'), isFalse);
+      expect(builder.isWithin('foo/bar', 'foo/bar/baz'), isTrue);
+      expect(builder.isWithin('foo/bar', 'foo/baz'), isFalse);
+      expect(builder.isWithin('foo/bar', '../path/foo/bar/baz'), isTrue);
+      expect(builder.isWithin('/', '/foo/bar'), isTrue);
+      expect(builder.isWithin('baz', '/root/path/baz/bang'), isTrue);
+      expect(builder.isWithin('baz', '/root/path/bang/baz'), isFalse);
+    });
+
+    test('from a relative root', () {
+      var r = new path.Builder(style: path.Style.posix, root: 'foo/bar');
+      expect(builder.isWithin('.', 'a/b/c'), isTrue);
+      expect(builder.isWithin('.', '../a/b/c'), isFalse);
+      expect(builder.isWithin('.', '../../a/foo/b/c'), isFalse);
+      expect(builder.isWithin('/', '/baz/bang'), isTrue);
+      expect(builder.isWithin('.', '/baz/bang'), isFalse);
+    });
+  });
+
   group('resolve', () {
     test('allows up to seven parts', () {
       expect(builder.resolve('a'), '/root/path/a');
       expect(builder.resolve('a', 'b'), '/root/path/a/b');
       expect(builder.resolve('a', 'b', 'c'), '/root/path/a/b/c');
       expect(builder.resolve('a', 'b', 'c', 'd'), '/root/path/a/b/c/d');
       expect(builder.resolve('a', 'b', 'c', 'd', 'e'), '/root/path/a/b/c/d/e');
       expect(builder.resolve('a', 'b', 'c', 'd', 'e', 'f'),
           '/root/path/a/b/c/d/e/f');
       expect(builder.resolve('a', 'b', 'c', 'd', 'e', 'f', 'g'),
@@ skipping 52 matching lines @@
     expect(builder.toUri('/'), Uri.parse('file:///'));
     expect(builder.toUri('foo/bar'), Uri.parse('foo/bar'));
     expect(builder.toUri('/path/to/foo#bar'),
         Uri.parse('file:///path/to/foo%23bar'));
     expect(builder.toUri(r'/_{_}_`_^_ _"_%_'),
         Uri.parse('file:///_%7B_%7D_%60_%5E_%20_%22_%25_'));
     expect(builder.toUri(r'_{_}_`_^_ _"_%_'),
         Uri.parse('_%7B_%7D_%60_%5E_%20_%22_%25_'));
   });
 }