teach find git refs to find commits that change a file or files

[g-k]

e.g. output commits from git log --format=oneline --follow -- package-lock.json

https://stackoverflow.com/questions/3701404/how-to-list-all-commits-that-changed-a-specific-file

Might be useful for repos without tags.

This was used in a paper, but I can't remember which one.