I want to filter @github email notifications based on two things: 1. whether it's an issue I've interacted with or I'm getting the email just because I'm subscribed to notifications for the repository 2. what repository it is.

the sidebar of the web UI does this fwiw

BUT i'm pretty sure you can do this via email as well, just not in gmail. `X-GitHub-Reason:` is the header for why you got pinged (mention vs subscribed vs whatever). For mentions `Mention <mention@noreply.github.com>` will also be in the `To:`

As for filtering by repo, there's a List-ID header set. I'm not sure if this can be filtered on in Gmail