Merge branch 'js/retire-preserve-merges'

The "--preserve-merges" option of "git rebase" has been removed. * js/retire-preserve-merges: sequencer: restrict scope of a formerly public function rebase: remove a no-longer-used function rebase: stop mentioning the -p option in comments rebase: remove obsolete code comment rebase: drop the internal `rebase--interactive` command git-svn: drop support for `--preserve-merges` rebase: drop support for `--preserve-merges` pull: remove support for `--rebase=preserve` tests: stop testing `git rebase --preserve-merges` remote: warn about unhandled branch.<name>.rebase values t5520: do not use `pull.rebase=preserve`