Filter md

Author: janhohenheim

.github/workflows/ci.yml

@@ -23,10 +23,12 @@ jobs:
       # source: https://stackoverflow.com/a/74268200
       run: |
         if ${{ github.event_name == 'pull_request' }}; then
-            echo "changed_files=$(git diff --name-only -r HEAD^1 HEAD | xargs)" >> $GITHUB_OUTPUT
+            changed_files=$(git diff --name-only -r HEAD^1 HEAD | xargs)
         else
-            echo "changed_files=$(git diff --name-only ${{ github.event.before }} ${{ github.event.after }} | xargs)" >> $GITHUB_OUTPUT
+            changed_files=$(git diff --name-only ${{ github.event.before }} ${{ github.event.after }} | xargs)
         fi
+        # filter out files that are not markdown
+        echo "changed_files=$(echo $changed_files | tr ' ' '\n' | grep -E '\.md$' | xargs)" >> $GITHUB_OUTPUT
     - name: Lint
       uses: avto-dev/markdown-lint@v1
       with: