third party crate support with mirror file path

[zhiyuan-liao]

I'm using a rust crate mirror links: mirrors.ustc.edu.cn and racer with vim YCM
when I update dependents library, the third party crate source code is just download into the .cargo/registry/src/mirrors.ustc.edu.cn-XXXX/ path.
but I found that, racer does not catch the right define of the crate code. just show Errors:
"RuntimeError: Can't jump to definition." how could I resolve this problem. any help will be appreciate, thanks.

[Shougo]

You can add the support for it.
I don't know about racer path implementation.