title: Enforce git merge.ff false on server side hook
body: <p>Our git workflow mandate that we always create a merge commit, even when it's a fast forward merge (simplify history reading without resorting to rebase).</p>
  
  <p>While conventions are good ("please run 'git config -add merge.ff false'"), I want to enforce that kind of logic on our git server using a hook. I've tried to think about the logic and got stuck. Any clue on how to implement that kind of logic? Any ready-made scripts?</p>