You’re right, I was definitely conflating PRs and issues in my last two posts! And you’re also right that it probably doesn’t make sense to have issues in elm-janitor/core – just PRs.
So let’s say we have issue elm/core#123, which has a proposed fix in PR elm/core#789, and that same fix is also submitted in PR elm-janitor/core#456. Then I think all that’s needed is fixes elm/core#123 in the commit message. I believe that’ll cause GH to auto-generate a note in the root issue elm/core#123 that references the elm-janitor/core#456 PR, because that PR’s text (taken from the commit message) will mention the issue.
That’s the key thing in my mind: people who run into an Elm bug are gonna find the original issue in the elm/* project, and if GH auto-generates that link, they’ll be able to make their way over to the elm-janitor PR and find instructions for how to make use of it in their project.
For example, I mentioned the elm/core#1018 PR in a commit on my project, and GH automatically created a link from the former to the latter. Admittedly the thing in elm/core was a PR, not an issue, but I’m pretty sure this mechanism works for either.