Fix --offline with prerelease versions.

lib/src/source/hosted.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.
 
 import 'dart:async';
 import 'dart:io' as io;
 import "dart:convert";
 
 import 'package:http/http.dart' as http;
 import 'package:path/path.dart' as path;
@@ skipping 253 matching lines @@
         "$systemCacheRoot/${_urlToDirectory(server)}");
 
     var dir = path.join(systemCacheRoot, _urlToDirectory(server));
 
     var versions;
     if (dirExists(dir)) {
       versions = await listDir(dir).map((entry) {
         var components = path.basename(entry).split("-");
         if (components.first != ref.name) return null;
         return HostedSource.idFor(
-            ref.name, new Version.parse(components.last),
+            ref.name, new Version.parse(components.skip(1).join("-")),
             url: _serverFor(ref.description));
       }).where((id) => id != null).toList();
     } else {
       versions = [];
     }
 
     // If there are no versions in the cache, report a clearer error.
     if (versions.isEmpty) {
       throw new PackageNotFoundException(
           "Could not find package ${ref.name} in cache.");
@@ skipping 108 matching lines @@
   var name = description["name"];
   if (name is! String) {
     throw new FormatException("The 'name' key must have a string value.");
   }
 
   var url = description["url"];
   if (url == null) url = HostedSource.defaultUrl;
 
   return new Pair<String, String>(name, url);
 }