actions: test cache/{restore,save}@v4 support

actions/example-cache/.forgejo/workflows/test.yml

@@ -0,0 +1,51 @@
+on: [push]
+
+jobs:
+  build:
+    runs-on: docker
+    container:
+      image: code.forgejo.org/oci/node:20-bookworm
+    steps:
+      - name: cache restore
+        id: cachestep1
+        uses: https://code.forgejo.org/actions/cache/restore@v4
+        with:
+          path: |
+            /usr/local/bin/something
+          key: cachekey
+
+      - name: cache hit
+        run: |
+          set -x
+          test "${{ steps.cachestep1.outputs.cache-hit }}" != true
+
+      - name: create something
+        run: echo SOMETHING > /usr/local/bin/something
+
+      - name: cache save
+        uses: https://code.forgejo.org/actions/cache/save@v4
+        with:
+          path: |
+            /usr/local/bin/something
+          key: ${{ steps.cachestep1.outputs.cache-primary-key }}
+
+      - name: remove something
+        run: rm /usr/local/bin/something
+
+      - name: cache restore
+        id: cachestep2
+        uses: https://code.forgejo.org/actions/cache/restore@v4
+        with:
+          path: |
+            /usr/local/bin/something
+          key: cachekey
+
+      - name: verify something
+        run: |
+          set -x
+          test SOMETHING = $(cat /usr/local/bin/something)
+
+      - name: cache hit
+        run: |
+          set -x
+          test "${{ steps.cachestep2.outputs.cache-hit }}" = true