Create a ComboIndexCache from registry name?

[MarijnS95]

In case of a publishing tool like cargo smart-release --registry xxx, individual crates via the [package] publish = ["xxx"] attribute, or [registry] default = "xxx" in .cargo/config.toml, users specify a registry by name which resolve to a registry defined via env vars or in the .cargo/config.toml [regitries] table.

Since this crate already seems to have some support to parse .cargo/config.toml (and follows precedence order), would it be possible to get constructors for ComboIndexCache (and/or one of the IndexLocation/IndexUrl types) with the name of a registry, and automatically piece together the URL from that?

As a side-quest, note also that the existing [source] replace-with functionality can also point to such named [registries].

Note that this request, together with many more issues, was first asked at the crate tame-index was hard-forked from: frewsxcv/rust-crates-index#168. Most of the issues described there seem to have already been addressed here, which is why I'm investigating whether tame-index could be a sensible replacement for rust-crates-index.

[MarijnS95]

Thanks for the very quick solution @Jake-Shadle! I'll queue this up to replace rust-crates-index in cargo-smart-release with tame-index as that's exactly where I'll need this.