A library called crate is usable (with nightly Cargo) but just annoying.
// ```toml
// cargo-features = ["rename-dependency"]
//
// [package]
// name = "testing"
// version = "0.0.0"
//
// [dependencies]
// renamed_crate = { package = "crate", version = "0.0.2" }
// ```
extern crate renamed_crate;
fn main() {}