Merge branch 'en/rebase-incompatible-opts'

"git rebase" often ignored incompatible options instead of complaining, which has been corrected. * en/rebase-incompatible-opts: rebase: provide better error message for apply options vs. merge config rebase: put rebase_options initialization in single place rebase: fix formatting of rebase --reapply-cherry-picks option in docs rebase: clarify the OPT_CMDMODE incompatibilities rebase: add coverage of other incompatible options rebase: fix incompatiblity checks for --[no-]reapply-cherry-picks rebase: fix docs about incompatibilities with --root rebase: remove --allow-empty-message from incompatible opts rebase: flag --apply and --merge as incompatible rebase: mark --update-refs as requiring the merge backend