This seems like a duplicate of #39630 cc @julieqiu

I might have spoken too early. It seems like the problem isn't that links aren't versioned, but rather that master gets replaced with a specific pseudo-version. I think that's on purpose, so that the links are stable and don't change over time - which is also a reasonable use case.

Would you provide both as an option? If so, how?

Hmm, the development branches are inherently not stable so users won't expect to have stability when browsing branches. Not being able to use the package site during development is a more major issue in our case.

Pehraps GitHub's model could be copied here. The links are as-is by default, e.g. master in most cases when opening a repo for the first time. And you can press y while looking at a specific path to replace that branch name with a fully expanded commit hash.

Though I have to say that such a default worries me a little bit. Far too often people share GitHub links with just "master" as the ref, which tends to break over time. Especially now that many projects are renaming their master branch :)

I have one more idea but not sure if it's a good one.

Development-time package serving can a separate service clearly indicating that it's not the stable thing.
http://unstable.pkg.go.dev/go.opentelemetry.io/otel

Another way to implement that could be just a URL query parameter like ?unstable, which might be less invasive.