Add pub (and by extension YAML) to the SDK.

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('pub_io');
 
 #import('dart:io');
 
-#import('../lib/file_system.dart', prefix: 'fs');
-
 /** Gets the current working directory. */
 String get workingDir() => new File('.').fullPathSync();
 
 /**
  * Joins a number of path string parts into a single path. Handles
  * platform-specific path separators. Parts can be [String], [Directory], or
  * [File] objects.
  */
 String join(part1, [part2, part3, part4]) {
   final parts = _getPath(part1).split('/');
@@ skipping 14 matching lines @@
     }
   }
 
   return Strings.join(parts, Platform.pathSeparator());
 }
 
 /**
  * Gets the basename, the file name without any leading directory path, for
  * [file], which can either be a [String], [File], or [Directory].
  */
+// TODO(rnystrom): Copied from file_system (so that we don't have to add
+// file_system to the SDK). Should unify.
 String basename(file) {
-  return fs.basename(_getPath(file));
+  file = _getPath(file).replaceAll('\\', '/');
+
+  int lastSlash = file.lastIndexOf('/', file.length);
+  if (lastSlash == -1) {
+    return file;
+  } else {
+    return file.substring(lastSlash + 1);
+  }
 }
 
 /**
  * Asynchronously determines if [file], which can be a [String] file path or a
  * [File], exists on the file system. Returns a [Future] that completes with
  * the result.
  */
 Future<bool> fileExists(file) {
   final completer = new Completer<bool>();
 
@@ skipping 258 matching lines @@
 }
 
 /**
  * Gets a [Directory] for [entry], which can either already be one, or be a
  * [String].
  */
 Directory _getDirectory(entry) {
   if (entry is Directory) return entry;
   return new Directory(entry);
 }