This is a boring message about some really minor things.

While working on "guix" shell completions, I noticed that "--help"
messages want some nitpicking.

I think that formatting of system actions should be adjusted to the
formatting of guix subcommands and importers (an aligned list of
commands).  What about a newline between a description line and
commands?  Should it be there (as in ‘guix --help’ now) or not (as in
‘guix import --help’)?

--8<---------------cut here---------------start------------->8---
Some description here:

   some
   commands
   here
--8<---------------cut here---------------end--------------->8---

The patch is attached, thanks.