I think it's fair to use this as supporting evidence. If they are assigned tasks that aren't too difficult and they aren't completing them really fast, and ther

I think it's fair to use this as supporting evidence. If they are assigned tasks that aren't too difficult and they aren't completing them really fast, and there is a PR process in which changes are landed into the repo, then I think it's fair to use the number of commits to the repo. If anybody can push commits to the repo, then it's a useful metric. Finally, this sort of action should be take after the manager has worked with their report, by having somebody else help them, or put them on a different project.