systemd-based initramfs for NixOS

This is an experimental attempt to reimplement the stage-1 initramfs of NixOS so that it is managed by systemd rather than boring shell scripts.

Use

• Currently the primary way of building this initramfs is just nix-build in the root of the repository.

• But it is also possible to import the modules from this repository into your regular NixOS config and build it normally:

  # /etc/nixos/configuration.nix
  {
    imports = [
      # ... other imports ...
    ]
    ++ import /path/to/nixos-init/modules/module-list.nix;
  
    # ...
  }