Merkle trees and build systems

The differences you talked about: hashing the content of intermediate build steps and using Merkle hashing for deduplication/incrementally have long been things we've wanted to try with Nix, as you've noticed.

What's new is that we're now doing it! The company I working on IPFS and Nix, as described in https://discourse.nixos.org/t/obsidian-systems-is-excited... . The underlying changes should make it easy to support other hashing schemes like OSTree's.

I'm really glad to see you all are working on similar things---the shift in perspective from rules on files to rules on subtrees is huge and I hope to see it emerge and spread in as many ways is possible. Hopefully everyone can modularize and we're have more interopt / drop-in replacements and independent composition of networking and storage methods.

Happy to answer any questions about Nix / would love to compare notes on these sorts of things.