Make pub use the SDK's "version" file for its version.

utils/pub/pub.dart

Index: utils/pub/pub.dart
diff --git a/utils/pub/pub.dart b/utils/pub/pub.dart
index ac700f9b0de439d4c1e31ad157f806abaa6e4e62..03dab4467b1d62bf875547dcfc95ffef2962e42c 100644
--- a/utils/pub/pub.dart
+++ b/utils/pub/pub.dart
@@ -23,14 +23,13 @@ import 'exit_codes.dart' as exit_codes;
 import 'log.dart' as log;
 import 'package.dart';
 import 'pubspec.dart';
+import 'sdk.dart' as sdk;
 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);
-
 /// The commands that Pub understands.
 Map<String, PubCommand> get pubCommands {
   var commands = {
@@ -172,7 +171,7 @@ void printUsage([String description = 'Pub is a package manager for Dart.']) {
 }
 
 void printVersion() {
-  log.message('Pub $pubVersion');
+  log.message('Pub ${sdk.version}');
 }
 
 abstract class PubCommand {