"git rebase --signoff" used to forget that it needs to add a
sign-off to the resulting commit when told to continue after a
conflict stops its operation.
* pw/rebase-m-signoff-fix:
rebase -m: fix --signoff with conflicts
sequencer: store commit message in private context
sequencer: move current fixups to private context
sequencer: start removing private fields from public API
sequencer: always free "struct replay_opts"