We are using trac and are really satisfied with it. However, out of the box, trac is best suited for single-project environments only. I'd be interested to hear about the various approaches people take to make it work with multiple projects nevertheless and their experiences with them. Are there any plugins to recommend? Any patches, tweaks or whatnots? Are you maybe even using an entirely different bug-tracking system that offers all of trac's functionality plus multi-project support?

We recently started managing a second project ourselves which generally works okay but also has some drawbacks, especially where the two projects overlap because of common library code we wrote that is used in both projects. How do you handle this?

(I'll attach our own current approach as an answer to this post.)