Today was mostly spent driving across Brazil, but I had energy this evening for a little work on git-annex.

Made the assistant delete old temporary files on startup. I've had scattered reports of a few users whose .git/annex/tmp contained many files, apparently put there by the assistant when it locks down a file prior to annexing it. That seems it could possibly be a bug -- or it could just be unclean shutdowns interrupting the assistant. Anyway, this will deal with any source of tmp cruft, and I made sure to preserve tmp files for partially downloaded content.