Use Default branch instead of expecting main

worker-{{cookiecutter.slug}}/ci/build.sh

@@ -20,7 +20,7 @@ cd $CI_PROJECT_DIR
 docker build -f Dockerfile . -t "$IMAGE_TAG"
 
 # Publish the image on the main branch or on a tag
-if [ "$CI_COMMIT_REF_NAME" = "main" -o -n "$CI_COMMIT_TAG" ]; then
+if [ "$CI_COMMIT_REF_NAME" = "$CI_DEFAULT_BRANCH" -o -n "$CI_COMMIT_TAG" ]; then
   if [ -n "$CI_REGISTRY" -a -n "$CI_REGISTRY_USER" -a -n "$CI_REGISTRY_PASSWORD" ]; then
     echo $CI_REGISTRY_PASSWORD | docker login -u $CI_REGISTRY_USER --password-stdin $CI_REGISTRY
     docker push $IMAGE_TAG