> it's possible to hook into it in such a way that you can make it scale to ridiculous sizes (see e.g. https://bitbucket.org/facebook/remotefilelog) cleanly, in a fully backwards-compatible way, without forking the product.
That's not entirely true. For instance, some of the scaling is going to require a new manifest format that is not going to be backwards compatible.
That's not entirely true. For instance, some of the scaling is going to require a new manifest format that is not going to be backwards compatible.