Merge branch 'mz/push'

Merge branch 'mz/push'

* mz/push: (23 commits)
  Use new TransportException constructors
  Add new handy constructors to TransportException, PackProtocolException
  Don't accept RefSpec with null source for fetch
  Push command line utility
  Repository search for command line tools
  Test cases for RefSpec to RemoteRefUpdate conversions
  Test cases for PushProcess
  Transport* - general support for push() and implementations
  Add String versions of methods in RefSpec
  Clarify Repository#resolve() documentation
  Add PushProcess class implementing git-send-pack logic
  Fix: let RevWalk reset correctly before isMergedInto()
  Add BasePackPushConnection implementing git-send-pack protocol
  Add ignoreMissingUninteresting option to PackWriter
  Big refactor: *Connection hierarchy
  Support for fetchThin and pushThin options in Transport
  Add PushResult class
  Refactor: extract superclass OperationResult from FetchResult
  Add RemoteRefUpdate class
  New constructor without RefSpec for TrackingRefUpdate
  ...