* Replace `--show-rules` with a more common `--verbose` option to
show rule descriptions while `convert-ly` is running. Right
now, `--show-rules` only emits the rules but doesn't do a
conversion at the same time, which is rather useless IMHO. Not
sure whether my Python abilities are good enough to implement
this feature; anyway, this will be a separate merge request.
I don't fully agree with your second item. In the use cases I
described, I have used "convert-ly -s" without any input file, to
see the list of changes, so please keep a possibility to easily list
the rules without an input file.