{
  channelsNixosStable = {
    ref = "nixos-18.09";
    rev = "<% git ls-remote https://github.com/nixos/nixpkgs-channels nixos-18.09 | awk '{ print $1 }' | tr -d '\n' -%>";
  };
  channelsNixosUnstable = {
    ref = "nixos-unstable";
    rev = "<% git ls-remote https://github.com/nixos/nixpkgs-channels nixos-unstable | awk '{ print $1 }' | tr -d '\n' -%>";
  };
}