Write shell scripts with Rust

I've recently released rust-script-ext as a single dependency for use with rust-script.
rust-script-ext exposes utilities for writing scripts in Rust, things like error infrastructure, argument parsing, file IO, and invoking commands.
Writing scripts in Rust is pretty neat, and allows the scripts to grow painlessly.
Please raise and issue or PR if you want more functionality exposed in rust-script-ext, and any feedback is appreciated!