i.e. .git is not really useful there, neither is a .svn, excluding those would likely cover most used version control systems sufficiently. Parsing a .gitignore file would be icing on the cake.

Most likely following Rule would be sufficient: Exclude if matches /^\./ (i.e. starts with a dot)

I hope I'm not the only one using a vcs for my mods, but this could cut down the size as well by quite a bit.