Refactor Github Action per b/485167538

Author: benknutson-google

.github/workflows/docker.yml

@@ -31,13 +31,13 @@ jobs:
           # Change all uppercase to lowercase
           IMAGE_ID=$(echo $IMAGE_ID | tr '[A-Z]' '[a-z]')
           # Strip git ref prefix from version
-          VERSION=$(echo "${{ github.ref }}" | sed -e 's,.*/\(.*\),\1,')
+          VERSION=$(echo "${GITHUB_REF}" | sed -e 's,.*/\(.*\),\1,')
           # Strip "v" prefix from tag name
-          [[ "${{ github.ref }}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
+          [[ "${GITHUB_REF}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
           [ "$VERSION" == "main" ] && VERSION=next
           echo IMAGE_ID=$IMAGE_ID
           echo VERSION=$VERSION
           [ "$VERSION" == "merge" ] && exit 0
-          [[ "${{ github.ref }}" == "refs/tags/"* ]] && docker tag $IMAGE_NAME $IMAGE_ID:latest && docker push $IMAGE_ID:latest
+          [[ "${GITHUB_REF}" == "refs/tags/"* ]] && docker tag $IMAGE_NAME $IMAGE_ID:latest && docker push $IMAGE_ID:latest
           docker tag $IMAGE_NAME $IMAGE_ID:$VERSION
           docker push $IMAGE_ID:$VERSION