This looks like it will break if there is a space in the path. I know that's unlikely, but it does force us to discuss whether and how quoting/escaping is performed for the arguments to `:sh`.

You could also simplify this a touch by not dependending on scala-library; just hand-roll your `main` method and use `System.out.println`.

Finally, we should have a test that shows what happens with `:sh gobbledegook`. If that is too inconvenient to test in partest, perhaps because of an unstable stack trace, at least provide a transcript of a manual test.

I do sort of wonder whether this feature pays its weight, or whether we should just ask people to use `scala.sys.process`.