https://github.com/TheLocehiliosan/yadm/blob/master/yadm.md
...
alt    Create  symbolic  links  and  process  templates for any managed files matching the naming rules described in the ALTERNATES  and TEMPLATES  sections.
       It is usually unnecessary to run this command, as yadm automatically  processes  alternates  by  default.
       This  automatic behavior can be disabled by setting the configuration yadm.auto-alt to "false".

https://github.com/jluttine/nixos-configuration

    nix-shell -p yadm -p git -p gnupg1orig

    # -w <work-tree>
    # -Y,--yadm-dir
    #      Override the yadm directory.  yadm stores its data relative to this directory.
    yadm clone https://github.com/jluttine/nixos-configuration.git -w /etc/nixos -Y /etc/nixos/.yadm

    yadm -Y /etc/nixos/.yadm decrypt
    yadm -Y /etc/nixos/.yadm alt
    exit