ci: release docker in source only (#8971)

* ci: release docker in source only

* condition at job level

* condition over secrets

* Apply suggestions from code review

Co-authored-by: Tony <TonyRL@users.noreply.github.com>

Co-authored-by: Tony <TonyRL@users.noreply.github.com>

.github/workflows/docker-release.yml

@@ -12,8 +12,20 @@ on:
       - 'yarn.lock'
 
 jobs:
+  check-env:
+    runs-on: ubuntu-latest
+    outputs:
+      check-docker: ${{ steps.check-docker.outputs.defined }}
+    steps:
+      - id: check-docker
+        env:
+          DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
+        if: ${{ env.DOCKER_USERNAME != '' }}
+        run: echo "::set-output name=defined::true"
   release:
     runs-on: ubuntu-latest
+    needs: check-env
+    if: needs.check-env.outputs.defined == 'true'
     steps:
       - name: Checkout
         uses: actions/checkout@v2