Consider using margo for integration tests involving registries.

[suaviloquence]

Describe your use case

As part of the effort to write snapshot tests for cargo-semver-checks edge cases (see #846), we need to use a Cargo registry for some edge cases, for example when the baseline version is yanked as in #275. It is probably not ideal both in terms of stress on crates.io and testing speed to use the official crates.io registry.

Describe the solution you'd like

One alternative registry is margo, which is a tool that creates a (sparse) registry of static files, that can be hosted on any HTTP server. This would be better than using crates.io because it is a sparse registry, so we don't have to download the index, and it can also be hosted locally because it's just static files.

It looks like margo added support for yanking, so it would at least be sufficent for testing that edge case.

Alternatives, if applicable

There may be similar projects/alternative registries. We will also need to determine whether to host a test registry publicly (e.g., on GitHub pages, which would make our tests require internet access), locally (ad-hoc server on test run, which would be more complex), or a mix of the two.

Additional Context

No response

[obi1kenobi]

Using a GitHub pages test registry in a GitHub Actions CI job would be totally fine. I wouldn't add it in the suite that cargo test runs by default. But we have plenty of dedicated CI jobs that require internet access already and test for various regressions, and it's worked out reasonably so far.