Get rid of join() and encapsulate File and Directory in io.dart.

utils/pub/git_source.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 git_source;
 
 import 'dart:async';
+
+import '../../pkg/path/lib/path.dart' as path;
+
 import 'git.dart' as git;
 import 'io.dart';
 import 'package.dart';
 import 'source.dart';
 import 'source_registry.dart';
 import 'utils.dart';
 
 /// A package source that installs packages from Git repos.
 class GitSource extends Source {
   final String name = "git";
@@ skipping 17 matching lines @@
   Future<Package> installToSystemCache(PackageId id) {
     var revisionCachePath;
 
     return git.isInstalled.then((installed) {
       if (!installed) {
         throw new Exception(
             "Cannot install '${id.name}' from Git (${_getUrl(id)}).\n"
             "Please ensure Git is correctly installed.");
       }
 
-      ensureDir(join(systemCacheRoot, 'cache'));
+      ensureDir(path.join(systemCacheRoot, 'cache'));
       return _ensureRepoCache(id);
     }).then((_) => systemCacheDirectory(id)).then((path) {
       revisionCachePath = path;
       if (entryExists(revisionCachePath)) return;
       return _clone(_repoCachePath(id), revisionCachePath, mirror: false);
     }).then((_) {
       var ref = _getEffectiveRef(id);
       if (ref == 'HEAD') return;
       return _checkOut(revisionCachePath, ref);
     }).then((_) {
       return new Package.load(id.name, revisionCachePath, systemCache.sources);
     });
   }
 
   /// Returns the path to the revision-specific cache of [id].
   Future<String> systemCacheDirectory(PackageId id) {
     return _revisionAt(id).then((rev) {
       var revisionCacheName = '${id.name}-$rev';
-      return join(systemCacheRoot, revisionCacheName);
+      return path.join(systemCacheRoot, revisionCacheName);
     });
   }
   /// Ensures [description] is a Git URL.
   void validateDescription(description, {bool fromLockFile: false}) {
     // A single string is assumed to be a Git URL.
     if (description is String) return;
     if (description is! Map || !description.containsKey('url')) {
       throw new FormatException("The description must be a Git URL or a map "
           "with a 'url' key.");
     }
@@ skipping 66 matching lines @@
   /// Checks out the reference [ref] in [repoPath].
   Future _checkOut(String repoPath, String ref) {
     return git.run(["checkout", ref], workingDir: repoPath).then(
         (result) => null);
   }
 
   /// Returns the path to the canonical clone of the repository referred to by
   /// [id] (the one in `<system cache>/git/cache`).
   String _repoCachePath(PackageId id) {
     var repoCacheName = '${id.name}-${sha1(_getUrl(id))}';
-    return join(systemCacheRoot, 'cache', repoCacheName);
+    return path.join(systemCacheRoot, 'cache', repoCacheName);
   }
 
   /// Returns the repository URL for [id].
   ///
   /// [description] may be a description or a [PackageId].
   String _getUrl(description) {
     description = _getDescription(description);
     if (description is String) return description;
     return description['url'];
   }
@@ skipping 25 matching lines @@
     return description['ref'];
   }
 
   /// Returns [description] if it's a description, or [PackageId.description] if
   /// it's a [PackageId].
   _getDescription(description) {
     if (description is PackageId) return description.description;
     return description;
   }
 }