rust/rhg/src/main.rs

rhg: add Command trait for subcommands implemented by rhg

Normalizes the interface of the cli's commands

Differential Revision: https://phab.mercurial-scm.org/D8611

Differential Revision: https://phab.mercurial-scm.org/D8648

mod commands;
mod error;
mod exitcode;

fn main() {
    std::process::exit(exitcode::UNIMPLEMENTED_COMMAND)
}