Split Reference into a separate crate

[cgwalters]

Hi, any opinion on splitting https://github.com/oras-project/rust-oci-client/blob/main/src/reference.rs into a separate crate ("oci-reference" e.g.)? It'd be a natural thing to use in https://github.com/containers/containers-image-proxy-rs which is a different way to fetch container images but wraps with a Rust API.

[cgwalters]

Or actually, is there a reason this crate doesn't depend on https://github.com/containers/oci-spec-rs ? If it did then we could just move the reference type there, cc containers/oci-spec-rs#205

[flavio]

I've been thinking about moving Reference to a dedicated crate. I've a couple of project that just need this portion of the whole oci-client crate.

I would be fine moving the code to oci-spec-rs too.

What do you think @thomastaylor312 ?

[thomastaylor312]

This was already asked for in #102 and I am also completely fine with having the reference stuff be external from this crate. The main issue here is getting the time to do this. So I am completely on board with moving to the oci-spec-rs since it helps us avoid redefining types and makes things more unified. But it is going to be a major change that would also affect dependent projects. So we have to do the work to integrate oci-spec-rs into this repo, add the reference stuff into oci-spec-rs, and then cut a new release with a warning that the types are breaking.

I personally don't have time to do that in at least the next month, so if someone is willing to work on it, I'd be more than willing to review the PR and get it merged

[cgwalters]

First step in containers/oci-spec-rs#207