CI: Add GitLab CI to build and deploy

- Build every branch, but only deploy the main branch
- Deploy the main branch to next.hamburg.ccc.de

.gitlab-ci.yml

@@ -0,0 +1,34 @@
+stages:
+  - build
+  - deploy
+
+build-website:
+  stage: build
+  image: alpine
+  before_script:
+    - apk update
+    - apk add tzdata hugo coreutils curl jq
+  script:
+    - ./fetch-calendar.sh
+    - sed -i "s#baseURL = 'https://hamburg.ccc.de/'#baseURL = 'https://next.hamburg.ccc.de/'#" hugo.toml
+    - hugo
+  artifacts:
+    expose_as: "website build"
+    name: "website-build-$CI_COMMIT_REF_NAME-$CI_COMMIT_SHORT_SHA"
+    paths:
+      - public/
+    expire_in: 1 month
+
+deploy-website:
+  stage: deploy
+  image: alpine
+  before_script:
+    - apk update
+    - apk add rsync openssh
+  script:
+    - chmod 400 $NEXT_SSH_DEPLOY_KEY
+    - rsync -r --delete -e "ssh -i $NEXT_SSH_DEPLOY_KEY -o 'UserKnownHostsFile $SSH_KNOWN_HOSTS_FILE'" public/ ccchh-website-deploy@public-web-static-intern.hamburg.ccc.de:/var/www/next.hamburg.ccc.de/
+  rules:
+    - if: $CI_COMMIT_BRANCH == "main"
+      when: on_success
+    - when: never