There's now an "update branch" button for PRs. Please don't use it unless there's really a need to merge origin/master to the PR branch. The reason to avoid clicking on this button is that it also triggers a full CI build. That uses shared ASF resource quota and we don't want to unnecessarily increase the resource demand. This button is useful when the PR CI has run a long time ago. In that case, it's recommended to merge origin/master so that merging a PR with an old PR run doesn't cause regressions.