Merge branch 'cc/cherry-pick-ff'

* cc/cherry-pick-ff: revert: fix tiny memory leak in cherry-pick --ff rebase -i: use new --ff cherry-pick option Documentation: describe new cherry-pick --ff option cherry-pick: add tests for new --ff option revert: add --ff option to allow fast forward when cherry-picking builtin/merge: make checkout_fast_forward() non static parse-options: add parse_options_concat() to concat options