- This adds a configuration file for Lefthook which is more flexible
  and powerful than Overcommit.
- The only downside is that if gather the diff between `origin/master`
  and `HEAD` so if you didn't fetch `origin/master` for a long time,
  the checks might be done on more files than the one that you updated.
- Also, that means you need a origin remote.
Signed-off-by: Rémy Coutable <remy@rymai.me>