Update test workflow to test outputs

.github/workflows/clean_packages.yml

@@ -28,10 +28,29 @@ jobs:
     name: Then delete them
     runs-on: ubuntu-latest
     steps:
-      - name: Delete more than two weeks old
-        uses: sondrelg/container-retention-policy@v1
+      - name: Cache(d) image versions to skip
+        uses: actions/cache@v2
+        with:
+          path: skip-image-versions.txt
+          key: image-versions-to-skip
+
+      - name: Create file if it doesn't exist
+        run: touch skip-image-versions.txt
+        if: steps.cache-venv.outputs.cache-hit != 'true'
+
+      - name: Output file content
+        run: cat skip-image-versions.txt
+
+      - name: Delete images more than 2 seconds old
+        uses: sondrelg/container-retention-policy@main
         with:
           image-names: ghcr-retention-policy-test
           cut-off: 2 seconds ago UTC+2
           account-type: personal
           token: ${{ secrets.PAT }}
+
+      - name: Write skipped tags to cache
+        run: echo "${{ steps.arbitrary-id.outputs.needs-github-assistance }}" > skip-image-versions.txt
+
+      - name: Output file content
+        run: cat skip-image-versions.txt