Ask HN: How do you objectively measure productivity from a Git Repo?

I know measuring productivity from a Git Repo doesn’t give the full picture in a typical work environment.

But in a short term projects, say a month where lot of coding is expected. How do you objectively measure how well one has contributed just using Git Repo?

Also how do you rate a team members contribution subjectively? Like problem solver, team player rating between 1 to 5. Any other better way to do this?