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`
223a1bfb58