This is turning out to be mostly nix-managed nowadays
Clone the repo to ~/dev/dotfiles
sh <(curl -L https://nixos.org/nix/install) --darwin-use-unencrypted-nix-store-volume
$ nix-channel --add https://github.com/nix-community/home-manager/archive/release-20.09.tar.gz home-manager
$ nix-channel --update
$ nix-shell '<home-manager>' -A install
Then finally
HOME_MANAGER_CONFIG=~/dev/dotfiles/home-manager/home.nix home-manager switch
if you get some weird error about insecure zsh stuff:
compaudit | xargs chmod g-w