fix spell mistake for argument pre-inspection.

this is a tiny modification for spell mistake.
orig:
Ensure.ArgumentNotNullOrEmptyString(thirdKeyPart, "secondKeyPart");
now:
Ensure.ArgumentNotNullOrEmptyString(thirdKeyPart, "thirdKeyPart");
Add debugger display for RefSpec
Extended RemoteUpdater to update refspecs

Push/Pull Ref Specs can be updated via Remotes.Update(). The collections
can either be manipulated or replaced completely. Any changes are saved
immediately.