Currently, the non forked PRs such as Renovate will run `publish_snapshot` because `CIRCLE_PR_NUMBER` is not defined for PRs which are opened from non forked repos. Instead we add a filter to only run `publish_snapshot` on releasable branches. Example of run were the mentioned variable is not defined https://app.circleci.com/pipelines/github/angular/angular/32093/workflows/7c8c4cfc-e6f6-44fc-a6dc-a82a6ac862db/jobs/976611 PR Close #41877