I'm not happy with positional arguments at the moment. They do not fit nicely with the rest of the library and have a weird API. We need to reassess how they should work.

The problems are:

1. The positional arguments do not really fit in an enum.
2. The distribution of positional arguments cannot be dependent on options (see for instance what cp requires).
3. The ranges are unintuitive and have no "obvious" default value.