ci: ensure that there are only relative URLs

To make it work both in the primary repository's GitHub Pages as well as
in the forks' GitHub Pages, we really need the URLs to be specified as
relative ones. Make sure that this is the case in the CI builds.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/ci.yml

@@ -22,6 +22,16 @@ jobs:
     - name: run Hugo to build the pages
       run: hugo
 
+    - name: ensure that there are no absolute URLs
+      run: |
+        set -x
+        if git grep --untracked --no-exclude-standard "\\(href\|src\) *= *[\"']/" \
+          -- public/ ':^public/js/jquery*' >/tmp/abs-urls.txt
+        then
+          cat /tmp/abs-urls.txt
+          exit 1
+        fi
+
     - name: run Pagefind ${{ env.PAGEFIND_VERSION }} to build the search index
       run: npx -y pagefind@${{ env.PAGEFIND_VERSION }} --site public