Merge branch 'js/rebase-deprecate-preserve-merges'

A bit more leftover clean-up to deprepcate "rebase -p".

* js/rebase-deprecate-preserve-merges:
rebase docs: recommend `-r` over `-p`
docs: say that `--rebase=preserve` is deprecated
tests: mark a couple more test cases as requiring `rebase -p`

diff --cc Documentation/git-rebase.txt
Simple merge