only push packages for Docker builder if we are a push to master

.github/workflows/docker.yml

@@ -7,6 +7,8 @@ on: [push, pull_request, workflow_dispatch]
 jobs:
   containers:
     runs-on: ubuntu-latest
+    env:
+      PUSH_PACKAGES: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}
     steps:
       - uses: actions/checkout@v2
       - name: Setup Docker Buildx
@@ -16,12 +18,14 @@ jobs:
           version: latest
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v1
+        if: ${{ env.PUSH_PACKAGES }}
         with:
           registry: ghcr.io
           username: ${{ github.repository_owner }}
           password: ${{ secrets.GHCR_TOKEN }}
       - name: Login to Docker Hub
         uses: docker/login-action@v1
+        if: ${{ env.PUSH_PACKAGES }}
         with:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
@@ -37,7 +41,7 @@ jobs:
       - name: Build image
         uses: docker/build-push-action@v2
         with:
-          push: true
+          push: ${{ env.PUSH_PACKAGES }}
           builder: ${{ steps.buildx.outputs.name }}
           context: .
           file: ./scripts/docker/ubuntu/Dockerfile