doesn't need full fledged activitypub, just a common place to login

might just do it federated way of "here is my domain, here is DNS entry pointing to my identity server to talk with", that way it isn't even tied to single identity service, but a given user will need to use only single login for all of the servers.

> I think it would've been far easier to build a decent GUI around that flow, with some email integration + a patch preview tool, rather than adding activitypub, but oh well.

Check out Sourcehut (https://sourcehut.org/). It uses a mailing list-based workflow so contributing code or bug reports is relatively effortless and doesn't require a Sourcehut account.

Email-based approaches have far more issues than just needing to create an account. I would much rather have to create another account than deal with git send-email ever again. It's awful.