nixos/getty: add option to autologin once per boot

  baseArgs = [

    "--login-program" "${cfg.loginProgram}"

  ] ++ optionals (cfg.autologinUser != null) [

  ] ++ optionals (cfg.autologinUser != null && !cfg.autologinOnce) [

    "--autologin" cfg.autologinUser

  ] ++ optionals (cfg.loginOptions != null) [

    "--login-options" cfg.loginOptions

  ] ++ cfg.extraArgs;

  gettyCmd = args:

    "@${pkgs.util-linux}/sbin/agetty agetty ${escapeShellArgs baseArgs} ${args}";

    "${pkgs.util-linux}/sbin/agetty ${escapeShellArgs baseArgs} ${args}";

  autologinScript = ''

    otherArgs="--noclear --keep-baud $TTY 115200,38400,9600 $TERM";

    ${lib.optionalString cfg.autologinOnce ''

      autologged="/run/agetty.autologged"

      if test "$TTY" = tty1 && ! test -f "$autologged"; then

        touch "$autologged"

        exec ${gettyCmd "$otherArgs --autologin ${cfg.autologinUser}"}

      fi

    ''}

    exec ${gettyCmd "$otherArgs"}

  '';

in

        '';

      };

      autologinOnce = mkOption {

        type = types.bool;

        default = false;

        description = ''

          If enabled the automatic login will only happen in the first tty

          once per boot. This can be useful to avoid retyping the account

          password on systems with full disk encrypted.

        '';

      };

      loginProgram = mkOption {

        type = types.path;

        default = "${pkgs.shadow}/bin/login";

    systemd.services."getty@" =

      { serviceConfig.ExecStart = [

          "" # override upstream default with an empty ExecStart

          (gettyCmd "--noclear --keep-baud %I 115200,38400,9600 $TERM")

          # override upstream default with an empty ExecStart

          ""

          (pkgs.writers.writeDash "getty" autologinScript)

        ];

        environment.TTY = "%I";

        restartIfChanged = false;

      };