Add explicit features for gix backend

[ggwpez]

Update tame-index and integrate the latest change: EmbarkStudios/tame-index#66

This merge request is adding two features to allow downstream developers to select which gix backend to use. Since Rust unifies the feature of a crate when building it, and gix has two mutually exclusive features, the only way here seems to propagate this oddity and expose it in the features of this crate as well.

More concretely, this conflicts otherwise in our crate where we also pull in cargo which then always enables the curl backend.

[obi1kenobi]

This functionality is now available in v0.33.0!

[Lorak-mmk]

I think it is after this PR not possible to do cargo install cargo-semver-checks --no-default-features - it fails to compile. Is that expected? I can't find anything about this in release notes

[obi1kenobi]

Oops! 😅

In retrospect, yes, that's a breaking change. I should have called it out in the release notes!

I didn't realize it was breaking and @ggwpez might not have noticed it either.

The irony of a breaking change linter having an unexpected breaking change is not lost on me 😅 This is why I want cargo-semver-checks lints that can check manifests: https://rust-lang.github.io/rust-project-goals/2024h2/cargo-semver-checks.html

[obi1kenobi]

I have updated the release notes to mention this, and offer the updated command cargo install cargo-semver-checks --no-default-features --features gix-reqwest that reproduces the previous behavior.

Thanks for reporting this, and I'm sorry I broke your workflow!