Three become one?

Is there a better way to write:

  only:
    variables:
      - $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH

It’s repeated across many jobs in my .gitlab-ci.yml

.default_branch:
  rules:
    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH

job1:
  extends: [ ".default_branch" ]

job2:
  extends: [ ".default_branch" ]

job3:
  extends: [ ".default_branch" ]

You should use rules instead of only.