Merge branch 'jc/rebase-detach-fix'

"git rebase $base $non_branch_commit", when $base is an ancestor or the $non_branch_commit, modified the current branch, which has been corrected. * jc/rebase-detach-fix: rebase: set REF_HEAD_DETACH in checkout_up_to_date() rebase: use test_commit helper in setup