Merge branch 'bf/fetch-set-head-config'

"git fetch" honors "remote.<remote>.followRemoteHEAD" settings to tweak the remote-tracking HEAD in "refs/remotes/<remote>/HEAD". * bf/fetch-set-head-config: remote set-head: set followRemoteHEAD to "warn" if "always" fetch set_head: add warn-if-not-$branch option fetch set_head: move warn advice into advise_if_enabled fetch: add configuration for set_head behaviour