xflags!{/// Does stuff
////// Helpful stuff.
cmd helpful {/// With an arg.
optional src: PathBuf
/// Another arg.
////// This time, we provide some extra info about the
/// arg. Maybe some caveats, or what kinds of
/// values are accepted.
optional extra:String/// And a switch.
required -s,--switch
/// And even a subcommand!
cmd sub {/// With an optional flag. This has a really long
/// description which spans multiple lines.
optional -f,--flag
}}}