Merge branch 'mg/detached-head-report'

"git branch" on a detached HEAD always said "(detached from xyz)", even when "git status" would report "detached at xyz". The HEAD is actually at xyz and haven't been moved since it was detached in such a case, but the user cannot read what the current value of HEAD is when "detached from" is used. * mg/detached-head-report: branch: name detached HEAD analogous to status wt-status: refactor detached HEAD analysis