Sitecore Field: Multi-Root Treelist

On nearly every Sitecore site I’ve built, we’ve had a need to display 2 separate sections of the content tree in a single treelist field. The most common use-case being, having a folder to hold components local to the current item, and a shared folder for all items to use. Until now, I had never taken the time to take that code and make it generally applicable to any Sitecore site, opting to port the code from one site to another. So without further ado, the Multi-Root Treelist: