Implement tooling in Git to surface information about repository health

The Git team often has the problem that it is hard to get all required information from customers in order to root cause issues. Part of the problem is that Git itself does not provide the tooling to make information like this easily accessible. While tools like git-sizer exist, it exists outside of Git and may thus not be available. It may also not understand all the details of how a repo is structured.

It would be nice to implement such tooling upstream.