Add a fake shell command to avoid using cmd all the time

[mlainez]

Hi,

I've used this when debugging my Nerves system. It redirects all lines from IO.gets to cmd. It's simply more convenient when debugging the Buildroot part of new Nerves systems.

It might be useful to others.

[fhunleth]

Thanks for contributing this!

This is so simple and the fact that you find it useful, means that it's good to include.

Overall, I'd either prefer to make the IEx session more ergonomic or offer an alternative Erlang shell with an sh-like syntax that includes tab completion and handles ctrl+c.

I'm also going to pay more attention to what I do when porting, since I don't run cmd that much. From observing others, the only guess that I have is that I reach for the File module so that I can get path completion. cmd's lack of path completion especially when navigating /sys has been a big limitation for me.

The CI issues look easy and very specific to unique things in this project. Let me try to fix real quick and then I'll merge when CI passes.

[mlainez]

It would indeed be great to have a way to use IEx almost like a regular shell. Having all system binaries there by default and path completion with tab would be awesome. It's worth investigating.