It's an ugly module, needs lot of a refactoring, i mainly ported @dominictarr's [level-couch-sync][lcs] to a general sync module.
I did this because I'm trying to replicate npmjs registry to riak.
var sync = "";sync;
progress events, and you can even pause and resume syncing by calling
instance.feed.resume() methods. (It can be useful if data comes too fast).