ci: add a stage to deploy to gitlab machines

.gitlab-ci.yml

@@ -76,7 +76,6 @@ deploy:
     - nix --experimental-features 'nix-command flakes' run nixpkgs#colmena -- apply --on @active-dns
     - nix --experimental-features 'nix-command flakes' run nixpkgs#colmena -- apply --on @active-core
     - nix --experimental-features 'nix-command flakes' run nixpkgs#colmena -- apply --on @active
-    - nix --experimental-features 'nix-command flakes' run nixpkgs#colmena -- apply --on wheatly
   only:
     refs:
       - main
@@ -85,4 +84,23 @@ deploy:
       - machines/**/*
       - secrets/**/*
       - flake.*
-      - .gitlab-ci.yml
+      - .gitlab-ci.yml
+
+deploy_gitlab:
+  stage: deploy
+  needs:
+    - deploy
+  tags:
+    - nix
+  before_script:
+    # setup ssh key
+    - eval $(ssh-agent -s)
+    - echo "$DEPLOY_KEY" | tr -d '\r' | ssh-add - > /dev/null
+    - mkdir -p ~/.ssh
+    - chmod 700 ~/.ssh
+    # load nix environment
+    - . "$HOME/.nix-profile/etc/profile.d/nix.sh"
+    - git pull origin main
+  script:
+    - nix --experimental-features 'nix-command flakes' run nixpkgs#colmena -- apply --on @active-gitlab
+  when: manual