Fetch non-ff changes

Add a + to refspecs so that pushmanager will fetch the lastest branch, regardless of whether it is a fast forward.

https://www.kernel.org/pub/software/scm/git/docs/git-fetch.html

Also move remote adding into the fetch subsection.
Previously we had added a fetch flag to create_or_update_repo and moved fetch logic into it. 
The remote-adding is only relevant to fetch, so we can move it inside for a minor reduction in work done.