Refactor Source and SourceRegistry.

lib/src/command.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.
 
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
 
 import 'entrypoint.dart';
 import 'log.dart' as log;
 import 'global_packages.dart';
 import 'system_cache.dart';
 
 /// The base class for commands for the pub executable.
 ///
 /// A command may either be a "leaf" command or it may be a parent for a set
 /// of subcommands. Only leaf commands are ever actually invoked. If a command
 /// has subcommands, then one of those must always be chosen.
 abstract class PubCommand extends Command {
   SystemCache get cache {
-    if (_cache == null) {
-      _cache = new SystemCache.withSources(isOffline: isOffline);
-    }
+    if (_cache == null) _cache = new SystemCache(isOffline: isOffline);
     return _cache;
   }
   SystemCache _cache;
 
   GlobalPackages get globals {
     if (_globals == null) {
       _globals = new GlobalPackages(cache);
     }
     return _globals;
   }
@@ skipping 49 matching lines @@
   ///
   /// If the parsing fails, prints a usage message and exits.
   int parseInt(String intString, String name) {
     try {
       return int.parse(intString);
     } on FormatException catch (_) {
       usageException('Could not parse $name "$intString".');
     }
   }
 }