add content_sha256 hash checks

[jaimergp]

Closes #4762

Description

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[codspeed-hq]

CodSpeed Performance Report

Merging #5277 will not alter performance

_{Comparing jaimergp:content-hash (4e0f6dd) with main (4457362)}

Summary

✅ 3 untouched benchmarks

[wolfv]

I think this is cool. It would also work nicely with the new proposal for "rendered recipes" (conda/ceps#74).

On that note - should we continue adding features to conda-build without any standardization (e.g. CEP) process?

[jaimergp]

should we continue adding features to conda-build without any standardization (e.g. CEP) process?

I'm planning to submit a CEP. I opened this draft to explore what kind of things are needed for a stable yet robust logic, cross platform. Things like permissions and so on don't translate well to Windows.

[wolfv]

Awesome. Yeah, I also recently looked at a few content hash implementations in Rust but didn't find anything super convincing yet. There are a bunch though (https://crates.io/search?q=content%20hash)

[jaimergp]

So far the scheme I followed looks a lot like https://github.com/DrSLDR/dasher?tab=readme-ov-file#hashing-scheme. Things to standardize would be how the tree is sorted, the normalization of the path, the separators (to prevent this), and the allowed algorithms.

I've seen a few merkle tree based packages but we don't need all the proof stuff, or leaf querying; just comparing the root hash.

Maybe it could be implemented in a recursive way that doesn't involve obtaining the whole file tree beforehand if that increases performance or simplifies implementation elsewhere. IMO this feels like one of those CEPs that does require prototyping first to see which things have to be standardized.