feels like we could get started by replacing activation with something that runs the existing code through something like

[{action: "nixos.generation-symlink/set",
  target: "/nix/store/<system>"},
 {action: "nixos.legacy/activate-system",
  variant: "boot",
  target: "/nix/store/<system>"}]

In reply to @raitobezarius:matrix.org
anyone is welcome to work on that, but there's a lot of work involved into touching stc

and according to my reverse-engineered deployment script, these are the two necessary actions, to emulate nixos-rebuild:

  deploy-ssh-for = {
    type = "app";
    program = toString (pkgs.writeScript "deploy-ssh-for" ''
      #!${pkgs.stdenv.shell}
      set -eux
      configName=$1
      remote=root@$2
      action=$3
      shift 3
      if [ gc = "$action" ]
      then ssh -C $remote nix-collect-garbage "$@"
           exit 0
      fi
      configuration=$(nix build .#nixosConfigurations.$configName.config.system.build.toplevel --print-out-paths --no-link -L)
      nix-copy-closure $(if [ "''${1-}" != --direct ]; then echo --use-substitutes; fi) --gzip --to $remote $configuration
      if [ dry-run = "$action" ]
      then set +x
           echo "[dry-run] Would run these commands:"
           echo "    ssh -C $remote nix-env --profile /nix/var/nix/profiles/system --set $configuration"
           echo "    ssh -C $remote $configuration/bin/switch-to-configuration $action"
      else if [ build = "$action" ]
      then ssh -C $remote nix-env --profile /tmp/nixos-system --set $configuration
      else if [ boot = "$action" -o switch = "$action" ]
      then ssh -C $remote nix-env --profile /nix/var/nix/profiles/system --set $configuration
           ssh -C $remote $configuration/bin/switch-to-configuration $action
      else echo "Unknown action '$action'. Use one of: dry-run, boot, switch"
      fi fi fi
    '');
  };