Make VersionSolver source- and description-aware.

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('io.dart');
 #import('package.dart');
 #import('source.dart');
 #import('utils.dart');
@@ skipping 29 matching lines @@
             "Cannot install '${id.name}' from Git (${id.description}).\n"
             "Please ensure Git is correctly installed.");
       }
     });
   }
 
   /**
    * The package name of a Git repo is the name of the directory into which
    * it'll be cloned.
    */
-  String packageName(PackageId id) =>
-      basename(id.description).replaceFirst(const RegExp("\.git\$"), "");
+  String packageName(description) =>
+      basename(description).replaceFirst(const RegExp("\.git\$"), "");
 
   /**
    * Ensures [description] is a Git URL.
    */
   void validateDescription(description) {
     if (description is! String) {
       throw new FormatException("The description must be a git URL.");
     }
   }
 }