Merge branch 'pw/rebase-keep-empty-fixes'

"git rebase --keep-empty" still removed an empty commit if the other side contained an empty commit (due to the "does an equivalent patch exist already?" check), which has been corrected. * pw/rebase-keep-empty-fixes: rebase: respect --no-keep-empty rebase -i --keep-empty: don't prune empty commits rebase --root: stop assuming squash_onto is unset