CI: Post staging URL to PR once (on open event)

.forgejo/workflows/deploy.yaml

@@ -17,7 +17,7 @@ jobs:
     steps:
       - name: Pipeline info
         run: |
-          echo "Run triggered by ${{ gitea.event_name }} on ref ${{ github.ref_name }}"
+          echo "Run triggered by ${{ github.event_name }} (${{ github.event.action }}) on ref ${{ github.ref_name }}"
 
       - name: Install packages
         run: |
@@ -54,6 +54,16 @@ jobs:
         run: |
           echo "Deploying to staging.hamburg.ccc.de/pr${{ github.event.pull_request.number }}"
           rsync -v -r --delete -e "ssh -i deploykey.priv -o 'UserKnownHostsFile ./known_hosts'" public/ ccchh-website-deploy@public-web-static-intern.hamburg.ccc.de:/var/www/staging.hamburg.ccc.de/pr${{ github.event.pull_request.number }}/
+      - name: Deploy - Add comment to PR with staging URL
+        if: github.event_name == 'pull_request' && github.event.action == 'opened'
+        run: |
+          curl \
+            -X POST \
+            ${{ github.event.pull_request.base.repo.url }}/issues/${{ github.event.pull_request.number }}/comments \
+            -H "Content-Type: application/json" \
+            -H "Authorization: token $GITHUB_TOKEN" \
+            --data '{ "body": "You can view your changes at https://staging.hamburg.ccc.de/pr${{ github.event.pull_request.number }}/" }'
+
       - name: Deploy - Upload to prod
         if: github.event_name == 'push' && github.ref_name == 'main'
         run: |