Cronjob to check website is online

.github/workflows/webcheck.yaml

@@ -0,0 +1,53 @@
+name: Website alive and correct
+
+on:
+  schedule:
+    - cron: 30 8 * * 1-5
+    # 8:30am, Mon-Fri
+  workflow_dispatch:
+    # Also work manually with a button press in GitHub UI.
+
+env:
+  WEBSITE_URL: "https://www.hacksoc.org/"
+
+jobs:
+  webcheck:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          # Only need the latest commit
+          fetch-depth: 1
+          # And don't even need any files!
+          sparse-checkout: .
+
+      - name: Fetch website
+        id: curl
+        # If this step fails, likely some issue with DNS, HTTPS, or server not running.
+        run: curl $WEBSITE_URL -o index.html --connect-timeout 5 -sS 2>&1 | sed -e 's/^/OUTPUT=/;' >> $GITHUB_OUTPUT 
+
+      - name: Error message if cURL fails
+        if: failure()
+        # Hopefully displays a nicely formatted error
+        run: echo "::error title=cURL::${{ steps.curl.outputs.OUTPUT }}. This might mean that Runciman is offline"
+
+      - name: Check index.html was written correctly
+        run: stat index.html > /dev/null
+
+      - name: Get Git SHA of HEAD
+        run: git rev-parse main | sed -e 's/^/SHA=/;' >> $GITHUB_OUTPUT
+        # git rev-parse main -- gets the full SHA1 of the most recent commit to 'main' branch
+        # sed -e 's/^/SHA=/;' -- adds "sha=" to the start of the line. This is important because...
+        # >> $GITHUB_OUTPUT -- Store the output in a variable so we can use it later.
+        #                      See https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter
+        id: git_sha
+
+      - name: Search for Git SHA in fetched HTML
+        id: grep
+        # If this step fails, then the website is out-of-date.
+        run: grep ${{steps.git_sha.outputs.SHA}} index.html
+
+      - name: Error message if SHA mismatches
+        # Only run if this specific step failed.
+        if: failure() && steps.grep.conclusion == 'failure'
+        run: echo ::error title=SHA mismatch::The commit SHA ${{steps.git_sha.outputs.SHA}} was not found in index.html. This means that the live website is out-of-date with the main branch.