Github actions: default branch variable

Question

Is there any smart way to determine the default branch in GitHub actions?

Now I need to write something like:

on:
  push:
    branches:
      - master

is there a way to write something like the code below?

on:
  push:
    branches:
      - $default-branch

I tried to google but found nothing

Answer 1

$default-branch can be used in Workflow templates, but not in Workflows. The branch will become hard-coded in the Workflow upon initialization, and will have to be manually maintained. [1]

Blog post: https://github.blog/changelog/2020-07-22-github-actions-better-support-for-alternative-default-branch-names/

Answer 2

I accidentally found a really nice way to solve this. That evalutes to the branch name, e.g. master.

${{ github.event.repository.default_branch }}

Also, found out the hard way that that always() is side-effecting: my job was getting skipped if always() was not called even though the other clause was true.

This works to run a job only when running on default branch

  if: ${{ always() && format('refs/heads/{0}', ) == github.ref }}