Today I wondered, not for the first time, why there isn't a button on GitHub pull requests that says “merge the latest from main” or whatever your default branch is called.

It turns out, there can be! But it's a hidden feature of GitHub! The button is called “update branch” but it's off by default.

I can't find the original announcement of the “update branch” button, but here's a follow up post: https://github.blog/changelog/2022-02-03-more-ways-to-keep-your-pull-request-branch-up-to-date/

Here are the docs: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/keeping-your-pull-request-in-sync-with-the-base-branch

Here's how to turn on the “update branch” button, per repo, by checking the box called “always suggest updating pull request branches”: https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/managing-suggestions-to-update-pull-request-branches

Is there any downside to enabling the “update branch” button? Well, there are complaints that doing so could result in more CI runs. What if you could prevent people from making a merge commit by disabling that option?

On a related note, there's a button called “sync fork” that does something similar for forks specifically. It was announced at https://github.blog/changelog/2021-05-06-sync-an-out-of-date-branch-of-a-fork-from-the-web/ and the docs are here: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork