{
  config,
  lib,
  self,
  ...
}: let
  cfg = config.soispha.version;
in {
  options.soispha.version = {
    enable = lib.mkEnableOption "storing the git revision in /etc/nixos_git_rev";
  };
  config = lib.mkIf cfg.enable {
    environment.etc.nixos_git_rev = {
      text = builtins.toString (self.longRev
        or self.lastModified
        or "unknown");
    };
  };
}