actions: cache-pull-request: pull request and cache isolation (#1062)

Reviewed-on: https://code.forgejo.org/forgejo/end-to-end/pulls/1062
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.code.forgejo.org>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>

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

@@ -0,0 +1,94 @@
+on:
+  pull_request:
+    types:
+      - opened
+      - closed
+
+jobs:
+  save-cache:
+    runs-on: docker
+    container:
+      image: code.forgejo.org/oci/node:20-bookworm
+    steps:
+      - name: cache restore
+        id: cachestep1
+        uses: https://data.forgejo.org/actions/cache/restore@v4
+        with:
+          path: |
+            /usr/local/bin/something
+          key: cachekey-${{ forge.event.pull_request.head.repo.full_name }}
+
+      - name: cache hit
+        run: |
+          set -x
+          test "${{ steps.cachestep1.outputs.cache-hit }}" != true
+
+      - name: create something
+        run: echo SOMETHING > /usr/local/bin/something
+
+      - name: cache save
+        uses: https://data.forgejo.org/actions/cache/save@v4
+        with:
+          path: |
+            /usr/local/bin/something
+          key: ${{ steps.cachestep1.outputs.cache-primary-key }}
+
+  restore-cache:
+    runs-on: docker
+    needs: [save-cache]
+    container:
+      image: code.forgejo.org/oci/node:20-bookworm
+    steps:
+      - name: cache restore
+        id: cachestep2
+        uses: https://data.forgejo.org/actions/cache/restore@v4
+        with:
+          path: |
+            /usr/local/bin/something
+          key: cachekey-${{ forge.event.pull_request.head.repo.full_name }}
+
+      - 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
+
+  test:
+    runs-on: docker
+    needs: [restore-cache]
+    container:
+      image: code.forgejo.org/oci/node:20-bookworm
+      options: "--volume /srv/example:/srv/example"
+
+    steps:
+      - name: setup
+        shell: bash
+        run: |
+          set -x
+          test $FORGEJO_TOKEN = ${{ env.FORGEJO_TOKEN }}
+          test $FORGEJO_TOKEN = ${{ forge.token }}
+          export DEBIAN_FRONTEND=noninteractive ; apt-get -qq update ; apt-get install -y -qq curl git >& /dev/null
+          curl -sS -o /usr/local/bin/forgejo-curl.sh https://code.forgejo.org/forgejo/forgejo-curl/raw/branch/main/forgejo-curl.sh && chmod +x /usr/local/bin/forgejo-curl.sh
+          forgejo-curl.sh --token "$FORGEJO_TOKEN" login $FORGEJO_SERVER_URL
+          forgejo-curl.sh api_json $FORGEJO_SERVER_URL/api/v1/user
+
+      - name: determine if the PR is from a fork
+        id: forked
+        run: |
+          if test ${{ forge.event.pull_request.base.repo.full_name }} = ${{ forge.event.pull_request.head.repo.full_name }} ; then
+            echo value=false >> $FORGEJO_OUTPUT
+          else
+            echo value=true >> $FORGEJO_OUTPUT
+          fi
+
+      - name: save event
+        run: |
+          d=/srv/example/cache-pull-request/contexts/${{ forgejo.event.pull_request.head.repo.owner.username }}/$FORGEJO_EVENT_NAME
+          mkdir -p $d
+          cat > $d/forgejo-${{ forgejo.event.action }} <<'EOF'
+          ${{ toJSON(forgejo) }}
+          EOF