> I bet it already exists, but what about an issue tracker in plain text maintained by git itself?
I have an issue tracker file that can be added to a project. While it's technically plain text, the interface for the file ensures that a format is used, and the format ensures that changes reflect only a single ticket.
Just as long as no one edits the file using a different program, it will work just fine.
Don't think anyone uses it, though.