adds file path source to pub

utils/pub/path_source.dart

+// Copyright (c) 2013, 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_source;
+
+import 'dart:async';
+import 'io.dart';
+import 'package.dart';
+import 'pubspec.dart';
+import 'version.dart';
+import 'source.dart';
+import 'dart:io';
+
+
+/// A package source that installs packages from disk for development use

[Bob Nystrom, 2013/01/17 19:15:10]

Add a "." to make this a full sentence. Also instead of "from disk", how about
"from a given file path".

[Sam E, 2013/01/20 04:16:57]

Done.

[Sam E, 2013/01/20 04:16:57]

Done.

+class PathSource extends Source {
+  final String name = 'path';
+  final bool shouldCache = false;

[Bob Nystrom, 2013/01/17 19:15:10]

Type annotations aren't needed for final fields, so just:

final name = 'path';
final shouldCache = false;

[Sam E, 2013/01/20 04:16:57]

Done.

+
+  PathSource();

[Bob Nystrom, 2013/01/17 19:15:10]

I think you can remove this if it doesn't do anything.

[Sam E, 2013/01/20 04:16:57]

Done.

+
+  Future<Pubspec> describe(PackageId id) =>
+    Package.load(id.name, id.description, systemCache.sources).then(
+        (pkg) => pkg.pubspec);
+
+  Future<bool> install(PackageId id, String path) =>
+    createPackageSymlink(id.name, id.description, path).then((_) => true);
+
+  void validateDescription(description, {bool fromLockFile: false}) {
+    if (description is String) return;
+    throw new FormatException("The description must be a path string");

[Bob Nystrom, 2013/01/17 19:15:10]

How about flipping this logic around and using if (description is! String)
throw...

Also, make the message a full sentence with a ".".

[Sam E, 2013/01/20 04:16:57]

Done.

+  }
+}