We've got a bunch of changes that the tildes upstream doesn't have. Figure out what we've actually got (I know there was a little thrashing, especially with some of the early build and deployment steps). (This might be made easier by comparing the current repo state to the state just after the fork.)
Once we've got a list of our actual changes, figure out which of these are likely to be upstreamable. (This might be my job.)
Upstream 'em. (This also might be my job.)
Merge the latest version of tildes in, fixing conflicts as necessary.