PackRefs is not an expensive gitaly call - we want to
call it more often (than as part of full `gc`) because
it helps to keep number of refs files small - too many
refs file may be a problem for deployments with
slow storage.
Replaces all the explicit include metadata syntax in the specs (tag:
true) into the implicit one (:tag).
Added a cop to prevent future errors and handle autocorrection.
