First trial in a nix flake update CI

.gitlab-ci.yml

@@ -0,0 +1,22 @@
+default:
+    image: nixpkgs/nix-flakes
+
+update-nix-flakes:
+    # Based on: https://forum.gitlab.com/t/git-push-from-inside-a-gitlab-runner/30554/5
+    before_script:
+        - eval `ssh-agent -s`
+        - mkdir --mode=700 -p ~/.ssh
+        - ssh-keyscan "$CI_SERVER_HOST" >> ~/.ssh/known_hosts
+        - echo "$SSH_PUBLIC_KEY" >> ~/.ssh/id_rsa.pub
+        - echo "${SSH_PRIVATE_KEY}" | ssh-add -
+    script:
+        - git config --global user.email "nix-matlab-CI@doronbehar.com"
+        - git config --global user.name "Nix Matlab CI"
+        - git remote add ci ssh://git@$CI_SERVER_HOST/$CI_PROJECT_PATH.git
+        - type nix
+        - nix --version
+        - nix flake update
+        - git add .
+        - git status
+        - git commit --message "[skip ci] Automatic nix flake update by CI" || echo "No changes, nothing to commit!"
+        - git push ci HEAD:$CI_COMMIT_REF_NAME # Pushes to the same branch as the trigger