Update workflow branch checks

Author: chrisns

.github/workflows/docker.yml

@@ -13,14 +13,14 @@ jobs:
       - uses: docker/setup-qemu-action@29109295f81e9208d7d86ff1c6c12d2833863392 # v3.6.0
 
       - name: Login to dockerhub
-        if: github.ref == 'refs/heads/master'
+        if: github.ref == format('refs/heads/{0}', github.event.repository.default_branch)
         uses: docker/login-action@74a5d142397b4f367a81961eba4e8cd7edddf772 # v3
         with:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
 
       - name: Login to GitHub
-        if: github.ref == 'refs/heads/master'
+        if: github.ref == format('refs/heads/{0}', github.event.repository.default_branch)
         uses: docker/login-action@74a5d142397b4f367a81961eba4e8cd7edddf772 # v3.4.0
         with:
           registry: ghcr.io
@@ -40,9 +40,10 @@ jobs:
             type=edge,branch=$repo.default_branch
 
       - name: build+push
+        if: github.ref == format('refs/heads/{0}', github.event.repository.default_branch)
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
           platforms: linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64
-          push: ${{ github.ref == 'refs/heads/master' }}
+          push: ${{ github.ref == format('refs/heads/{0}', github.event.repository.default_branch) }}
           tags: ${{ steps.docker_meta.outputs.tags }}
           labels: ${{ steps.docker_meta.outputs.labels }}