See #97 and recently #130 too.
This allows the user to pass in options such as "--ignore '*.pyc'" to not list any files ending in '.pyc' in the output. It uses the Rust glob crate and currently does a simple split on pipe, without any escaping, so it’s not really *complete*, but is at least something.
Now when you do `--sort time` instead of saying "unknown option --sort
time" it will say "unknown options '--sort time' (choices: name...)"
with all legal options.
This also adds the legal values to the default help text.
The original options was becoming a bit unwieldy, and would have been even more so if I added the same amount of comments. So this commit splits it up.
There's no extra hiding going on here, or rearranging things within the module: (almost) everything now has to be marked 'pub' to let other sub-modules in the new options module to see it.
