Add a Pub source for pub.dartlang.org.

utils/pub/pub.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.
 
 /**
  * The main entrypoint for the pub command line application.
  */
 #library('pub');
 
 #import('io.dart');
 #import('command_install.dart');
 #import('command_list.dart');
 #import('command_update.dart');
 #import('command_version.dart');
 #import('entrypoint.dart');
 #import('git_source.dart');
 #import('package.dart');
 #import('pubspec.dart');
+#import('repo_source.dart');
 #import('sdk_source.dart');
 #import('source.dart');
 #import('source_registry.dart');
 #import('system_cache.dart');
 #import('utils.dart');
 #import('version.dart');
 
 Version get pubVersion() => new Version(0, 0, 0);
 
 main() {
@@ skipping 40 matching lines @@
 
     if (args[0] == '--version') {
       printVersion();
       return;
     }
   }
 
   var cache = new SystemCache(cacheDir);
   cache.sources.register(new SdkSource(sdkDir));
   cache.sources.register(new GitSource());
+  cache.sources.register(new RepoSource());
+  // TODO(nweiz): Make 'repo' the default once pub.dartlang.org exists
   cache.sources.setDefault('sdk');
 
   // Select the command.
   var command = commands[args[0]];
   if (command == null) {
     printError('Unknown command "${args[0]}".');
     printError('Run "pub help" to see available commands.');
     exit(64); // See http://www.freebsd.org/cgi/man.cgi?query=sysexits.
     return;
   }
@@ skipping 72 matching lines @@
     Package.load(workingDir, cache.sources).chain((package) {
       entrypoint = new Entrypoint(package, cache);
 
       try {
         var commandFuture = onRun();
         if (commandFuture == null) return new Future.immediate(true);
 
         return commandFuture;
       } catch (var error) {
         handleError(error);
+        return new Future.immediate(null);
       }
     }).handleException(handleError);
   }
 
   /**
    * Override this to perform the specific command. Return a future that
    * completes when the command is done or fails if the command fails. If the
    * command is synchronous, it may return `null`.
    */
   abstract Future onRun();
 }