Merge branch 'jl/remote-rm-prune' into maint

"git remote rm" and "git remote prune" can involve removing many refs at once, which is not a very efficient thing to do when very many refs exist in the packed-refs file. * jl/remote-rm-prune: remote prune: optimize "dangling symref" check/warning remote: repack packed-refs once when deleting multiple refs remote rm: delete remote configuration as the last