Automating PR generation

[Eloston]

I've played around a little with Actions to semi-automatically generate PRs: ungoogled-software/ungoogled-chromium-portablelinux@91c811d

I wonder if we can speed up some of the work here if we can do the same for all our Debian variants. Some considerations:

• debian_sid will be the most fragile. It won't work for this branch if we have non-trivial merge conflicts with upstream Debian (I say "non-trivial" because some of it could be automated with a little more effort; e.g. GN flag conflicts in debian/rules).
  • In the event that we can't fix all the conflicts or auto-refresh all the patches, maybe we can have the Workflow submit a Draft PR with all the patches it could upgrade. Then we can pull the changes from the PR and finish it off.
• We might only need two workflows: One to update debian_sid, and another to submit PRs for all the other downstream branches.
• Future scope: Have the Workflow periodically check if it can create a PR for debian_sid. Basically we'd need to check if Debian upstream and ungoogled-chromium have updated.

[ghost]

It only really makes sense to do this against debian_sid. The other branches get the bulk of the upstream fixes via a merge from debian_sid. I do it this way to reduce the difficulty of merging stuff since it was already resolved in debian_sid. It does mean I have to directly retrieve stuff for debian_buster as I remove those patches from debian_sid since nothing else uses them but it's not a big problem.

Personally I don't think there's much we can automate since the bulk of it has to be reviewed by hand on major upgrades. Though we could have something report when there's new tags we could update the submodule to or new changes in Debian upstream. There is some kind of scheduling trigger that works off of CRON syntax we could try for that.