Merge branch 'ps/fetch-cleanups'

Code clean-up.

* ps/fetch-cleanups:
  fetch: use `fetch_config` to store "submodule.fetchJobs" value
  fetch: use `fetch_config` to store "fetch.parallel" value
  fetch: use `fetch_config` to store "fetch.recurseSubmodules" value
  fetch: use `fetch_config` to store "fetch.showForcedUpdates" value
  fetch: use `fetch_config` to store "fetch.pruneTags" value
  fetch: use `fetch_config` to store "fetch.prune" value
  fetch: pass through `fetch_config` directly
  fetch: drop unneeded NULL-check for `remote_ref`
  fetch: drop unused DISPLAY_FORMAT_UNKNOWN enum value

Author: gitster