Merge branch 'em/checkout-orphan'

* em/checkout-orphan:
log_ref_setup: don't return stack-allocated array
bash completion: add --orphan to 'git checkout'
t3200: test -l with core.logAllRefUpdates options
checkout --orphan: respect -l option always
refs: split log_ref_write logic into log_ref_setup
Documentation: alter checkout --orphan description