[WIP, Pre-RFC] Federation

[newpavlov]

I guess this Pre-RFC tries to describe something similar to what I've proposed here:

Silo effect of alternative registries

I think that alternative registries should be able to mirror dependencies from other registries (with a potential renaming) and published crate must depend only on crates from its own registry (which could be mirrored from other one). The mirrored crate will have at least the following fields: name, name and registry from which its mirrored, name and registry of the source. The latter two usually will be the same, but it could be useful to allow chains of mirrors. As a consequence non-mirrored c…

In other words soni-registry/serde will be a mirror of crates-io/serde. Of course you will not be able to patch serde like this, to do it you will have to use [patch] section and redirect serde to its fork.