rust-gdb etc. wrapper documentation missing from --help, book, etc.

Hi.

rustup (at leaast I assume it's rustup, since it seems like it's a hardlink to .cargo/bin/rustup) provided a wrapper rust-gdb on my PATH. This wrapper is convenient, so thanks.

However. I can't find any documentation about it. Some digging did find me the Rustup Book (although that is not installed by rustup!) which seems to have no mention of it. rustup man rust-gdb said no manual is available. rustup --help doesn't mention it. rust-gdb --help simply runs gdb and so prints gdb's help.

I suggest that:

• Whenever rustup is called as rust-gdb or cargo or something, and the first argument is --help, it ought to print a message saying "hello I am actually rustup acting as a wrapper for foo" and explaining where to get more information.

• There should be some documentation of these wrapper aliases somewhere. At the very leas there should be a list of them in the Rustup Book.

• Ideally there should be a way to find out what the extra arguments or environment are without using strace. This could be important, for example, if a user wants to do something that the rustup wrapper doesn't have direct support for.

Start by tracing how rustup handles invocations through aliases such as rust-gdb and how --help is dispatched. Review the Rustup Book and existing command or wrapper documentation, then define the documented alias list and help behavior; done means users can find the wrappers and understand where their behavior is described.