additonal_dependencies isn't "rollback safe" #311

Using old pre-commit + a hook repo with additional_dependencies it'll happily create the repo without installing the additional dependencies. Upon upgrading to a newer pre-commit, it doesn't know that the additional dependencies aren't installed yet and will happily attempt to run in there (usually causing an executable to not be found). We need some way to signify when these have been installed in order for this to be rollable. A workaround is to pre-commit clean when upgrading, but that kinda is not the best (and especially confusing).