Allow overriding commands arbitrarily, from the configuration file

[frank-lenormand]

Hi,

I believe it’s not possible to override the Git commands run by Gitu (or defined new Gitu commands) from the configuration file:

https://github.com/altsem/gitu/blob/a0c2970/src/default_config.toml

This might be out of scope for the project, but I’d appreciate being able to define my own shortcuts, similarly to how I do it with tig.

Thanks!