Hey! It sounds like you're describing ori [1]. Be sure to read the paper [2] because the website is a bit sparse on info. It's still young but the syncing, cheap snapshots, auto backups, etc. have been really nice. (it's only encrypted over transport though, I wish it were encrypted locally too).

1: http://ori.scs.stanford.edu/ 2: http://dl.acm.org/ft_gateway.cfm?id=2522721&ftid=1403940&dwn...