Trying out structopt based on yoshuawuyt's example

main.rs

extern crate structopt;
#[macro_use]
extern crate structopt_derive;

use structopt::StructOpt;

#[derive(StructOpt, Debug)]
#[structopt()]
enum Cmds {
  #[structopt(name = "add")]
  /// Add a thing.
  Add {
    #[structopt(short = "i")]
    interactive: bool,
    #[structopt(short = "p")]
    patch: bool,
    files: Vec<String>,
  },
  #[structopt(name = "fetch")]
  /// Fetch a thing.
  Fetch {
    #[structopt(long = "dry-run")]
    dry_run: bool,
    #[structopt(long = "all")]
    all: bool,
    repository: Option<String>,
  },
  #[structopt(name = "commit")]
  /// Commit a thing.
  Commit {
    #[structopt(short = "m")]
    message: Option<String>,
    #[structopt(short = "a")]
    all: bool,
  },
}

fn main() {
  let mut args = Cmds::from_args();
  match &args {
    &Cmds::Add { .. } => {
      // this is where we'd pass the struct to some_function
      // I thought this would require NLL, but it seems not!
      do_mut(&mut args);
    }
    &Cmds::Fetch { .. } => {
      // this is where we'd pass the struct to some_other_function
      println!("{:?}", args);
    }
    &Cmds::Commit { .. } => {
      println!("Commit: {:?}", args);
    }
  };
}

/// Some fn that takes a mutable reference.
fn do_mut(arg: &mut Cmds) {
    // Do something here.
    println!("Args are: {:?}", arg);
}