Add support for replaced source in Cargo config.toml

[nc7s]

Solves #44. The method name could be discussed - I just made up one.

[kornelski]

Thanks!

I think it should be in the new_cargo_default, instead of requiring every user of the crate to support it manually.

It would be nice if it searched for the config in the same way as cargo does.

[nc7s]

Where to put this is up to you ;)

It's not in the same way in regard to other kinds of sources other than registry. Kinda late here, will try implementing them later.

[nc7s]

Not sure what Index::with_path() is about; it seems to be a Git source in cargo's terms?

[kornelski]

I'd leave it just for the new_cargo_default. Other methods don't promise to behave like Cargo. If someone gives a custom path, then it's their problem.

[nc7s]

Then what exactly is "search for the config in the same way as cargo does"?

[kornelski]

https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure

[nc7s]

Ah, can't imagine how I ignored this… will do.