Fix issue 7215 by relativising a path before checking its components.

utils/pub/io.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.
 
 /**
  * Helper functionality to make working with IO easier.
  */
 library io;
 
 import 'dart:io';
@@ skipping 56 matching lines @@
 }
 
 // TODO(nweiz): move this into path.dart.
 /// Splits [path] into its individual components.
 List<String> splitPath(path) => _sanitizePath(path).split('/');
 
 /// Returns whether or not [entry] is nested somewhere within [dir]. This just
 /// performs a path comparison; it doesn't look at the actual filesystem.
 bool isBeneath(entry, dir) {
   var relative = relativeTo(entry, dir);
-  return !path.isAbsolute(relative) && !relative.startsWith('..');
+  return !path.isAbsolute(relative) && splitPath(relative)[0] != '..';
 }
 
 // TODO(nweiz): move this into path.dart.
 /// Returns the path to [target] from [base].
 String relativeTo(target, base) =>
   new path.Builder(root: base).relative(target);
 
 /**
  * Asynchronously determines if [path], which can be a [String] file path, a
  * [File], or a [Directory] exists on the file system. Returns a [Future] that
@@ skipping 1022 matching lines @@
   return new Directory(entry);
 }
 
 /**
  * Gets a [Uri] for [uri], which can either already be one, or be a [String].
  */
 Uri _getUri(uri) {
   if (uri is Uri) return uri;
   return new Uri.fromString(uri);
 }