Bring in the latest pub.

CHANGELOG.md

 ## 1.19.0
 
 ### Tool Changes
 
 * Pub
   * Added the ability for packages to declare a constraint on the [Flutter][]
     SDK:
 
         environment:
           flutter: ^0.1.2
           sdk: >=1.19.0 <2.0.0
 
     A Flutter constraint will only be satisfiable when pub is running in the
     context of the `flutter` executable, and when the Flutter SDK version
     matches the constraint.
 
   * Added `sdk` as a new package source that fetches packages from a hard-coded
     SDK. Currently only the `flutter` SDK is supported:
 
         dependencies:
           flutter_driver:
             sdk: flutter
             version: ^0.0.1
 
     A Flutter `sdk` dependency will only be satisfiable when pub is running in
     the context of the `flutter` executable, and when the Flutter SDK contains a
     package with the given name whose version matches the constraint.
 
+  * `tar` files on Linux are now created with `0` as the user and group IDs.
+    This fixes a crash when publishing packages while using Active Directory.
+
   * Fixed a bug where packages from a hosted HTTP URL were considered the same
     as packages from an otherwise-identical HTTPS URL.
 
   * Fixed timer formatting for timers that lasted longer than a minute.
 
   * Eliminate some false negatives when determining whether global executables
     are on the user's executable path.
 
 [Flutter]: https://flutter.io/
 
@@ skipping 1033 matching lines @@
     they will keep the Dart process alive until they time out. This fixes the
     handling of persistent connections. Previously, the client would shut down
     immediately after a request.
 
   * **Breaking change:** `HttpServer` no longer compresses all traffic by
     default. The new `autoCompress` property can be set to `true` to re-enable
     compression.
 
 * `dart:isolate`: `Isolate.spawnUri` added the optional `packageRoot` argument,
   which controls how it resolves `package:` URIs.