feat: add flags for local and remote registries to clone from
feat: add flags for local and remote registries to clone from

This allows people to experiment with registries they're not familiar
with; some examples:

* `cargo clone <some-crate> --registry-url <url>` for links to remote
    registries' index repos, i.e.,
    `https://dl.cloudsmith.io/public/<org-or-username>/<repo>/cargo/index.git`.
* `cargo clone <some-crate> --alt-registry <registry-from-config>`,
      where `registry-from-config` is a key to one of the [alternate
      registry entries in Cargo
      configuration](https://doc.rust-lang.org/cargo/reference/registries.html#using-an-alternate-registry).
* `cargo clone <some-crate> --local-registry <path>` for [local registry
      sources](https://doc.rust-lang.org/cargo/reference/source-replacement.html#local-registry-sources).

JanLikar/cargo-clone