Merge branch 'jk/maint-checkout-orphan-check-fix'

"git checkout <branchname>" to come back from a detached HEAD state
incorrectly computed reachability of the detached HEAD, resulting in
unnecessary warnings.

* jk/maint-checkout-orphan-check-fix:
  checkout: don't confuse ref and object flags

diff --cc builtin/checkout.c
Simple merge