If I had the time, which I don't, there are many things I would fix about fossil. Behavior when full is high on the list, as is the ability to specify a score in a create command. Fossil, in contrast to most Plan 9 programs, was a collaborative effort, which meant that no one understood the whole picture for too long.
If anyone does have time and wants to work on these problems, I am always happy to provide guidance. Russ
