build action & add jobs to Tests workflow for only-restore option

* add regular & proxy server jobs
* run job between save & restore jobs to test that only-restore option
  works with consecutive restores

.github/workflows/workflow.yml

@@ -71,6 +71,30 @@ jobs:
         path: |
           test-cache
           ~/test-cache
+  test-only-restore:
+    needs: test-restore
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macOS-latest]
+      fail-fast: false
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v3
+    - name: Restore cache
+      uses: ./
+      with:
+        only-restore: true
+        key: test-${{ runner.os }}-${{ github.run_id }}
+        path: |
+          test-cache
+          ~/test-cache
+    - name: Verify cache files in working directory
+      shell: bash
+      run: __tests__/verify-cache-files.sh ${{ runner.os }} test-cache
+    - name: Verify cache files outside working directory
+      shell: bash
+      run: __tests__/verify-cache-files.sh ${{ runner.os }} ~/test-cache
   test-restore:
     needs: test-save
     strategy:
@@ -118,6 +142,30 @@ jobs:
       with:
         key: test-proxy-${{ github.run_id }}
         path: test-cache
+  test-proxy-only-restore:
+    needs: test-proxy-save
+    runs-on: ubuntu-latest
+    container:
+      image: ubuntu:latest
+      options: --dns 127.0.0.1
+    services:
+      squid-proxy:
+        image: datadog/squid:latest
+        ports:
+          - 3128:3128
+    env:
+      https_proxy: http://squid-proxy:3128
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v3
+    - name: Restore cache
+      uses: ./
+      with:
+        only-restore: true
+        key: test-proxy-${{ github.run_id }}
+        path: test-cache
+    - name: Verify cache
+      run: __tests__/verify-cache-files.sh proxy test-cache
   test-proxy-restore:
     needs: test-proxy-save
     runs-on: ubuntu-latest