Merge branch 'cn/fetch-prune-overlapping-destination'

Merge branch 'cn/fetch-prune-overlapping-destination'

Protect refs in a hierarchy that can come from more than one remote
hierarcies from incorrect removal by "git fetch --prune".

* cn/fetch-prune-overlapping-destination:
  fetch: handle overlaping refspecs on --prune
  fetch: add a failing test for prunning with overlapping refspecs