Support "--ff" in cherry-pick API
Problem to solve
Analysis between branches always costs.
To reduce the differential between branches, we better keep them as tight as possible.
Using --ff with cherry-pick can avoid from unnecessary split if fast-forward is possible.
Intended users
Regular developers and project/branch integrators
User experience goal
The users should be able to add a parameter that equals to --ff when accessing with cherry_pick endpoint as the following
curl -XPOST -H "PRIVATE-TOKEN: <your_access_token>" --form "branch=dev" "https://gitlab.example.com/api/v4/projects/5/repository/commits/<sha1 on master>/cherry_pick?ff=true"