Require a description of changes on hotfix branch

[DMRobertson]

I noted in #11891 (c.f. #4826) that we don't really have a good idea of how the hotfixes branch differs to the releases branch. I propose that we require PRs against the hotfixes branch to include a changelog, and that we enforce this via a github action.

If we commit directly to the branch then this check is avoided. But that's not unique to this specific workflow.

Note that the Hotfixes workflow failed in 18f87a4 but suceeded in de277d8. The checks still fail overall in both cases because linting fails on matrix-org-hotfixes.

[richvdh]

I'm unconvinced. Changes to matrix-org-hotfixes often skip the PR phase, not least because they often happen in a hurry - which means the check will get skipped. I'd be hesitant to add obstacles to putting our stuff in git - better it goes in git with sketchy information than doesn't go in git at all.

A file such as you propose will be prone to getting out of date, and doesn't offer a whole lot more information than git logs do.

Rather, we should get rid of the differences (#4824), and then if we ever create a difference again, open a GH issue to track it and its removal.

[DMRobertson]

Rather, we should get rid of the differences (#4824), and then if we ever create a difference again, open a GH issue to track it and its removal.

My anxiety is that "we should create an issue" isn't enforced or automated, and so things will fall through the cracks. But I concede the suggestion here is pretty nuclear, and that

A file such as you propose [...] doesn't offer a whole lot more information than git logs do.

is pretty persuasive.