Why don't we have `libsync` yet?

An average Linux distro has about half a dozen file syncing libs. The source code we sync with git and other SCMs. But how can we sync some structured data? JSON, for example. Two-way, maybe in real time, for collaboration, revision control, and simply device syncing. As it turns out, there are challenges.

I will outline the history of the question and the ongoing efforts. Then, we will delve into the Replicated Data eXchange format (RDX) and the progress of librdx.