Preliminary support for sparse indices

[MoSal]

This will forever be a draft, unless someone adopts it of course. But I hope it will help moving things forward.

This implements preliminary support for sparse indices.

• All deps are updated/upgraded to latest versions.
• Git index support removed. Only sparse indices work.
• Tests are broken since they assume git indices.
• Crate info is not fetched in parallel for the sake of simplicity. Fetching is still very fast despite that (< 4s for cargo-edit, almost instantaneous with --offline).

ureq was already a dependency for some reason. So I used it after enabling the "gzip" feature.

Note to implementers regarding gix-based GitIndex from the latest crates_index:

• Some tests fail with hash mismatches.
• A test fails because the order of output is different (I think).
• Not sure how locking works with gix.

I didn't inspect those issues further, as I just wanted to make sparse indices work for me.

Related issues: #841, #865, #868, possibly #869

[amsam0]

git index support should probably be supported by reading the cargo config value, but it seems like a pain to find the config path so I can understand why you wouldn't want to add it, lol

[epage]

Something to keep in mind is that the FCP is about to close on merging parts of cargo-upgrade into cargo-update after which I'll get to work on doing that and it will be available in a nightly.

[MoSal]

@epage

Sounds good.

[tgross35]

@epage do you have a link to the proposal you mentioned? Wondering what the exact change is but can't find anything.

[epage]

https://github.com/rust-lang/cargo/issues/12425

I have a got a lot of the peripheral aspects done but haven't gotten to the core of it yet

[dvc94ch]

does this mean that cargo upgrade is broken for everyone that installed cargo/rust after the new registry format was added? how can I use the old registry format?

[dvc94ch]

what's the alternative right now? installing vscode and the rustrover plugin to update incompatible dependencies?