ln -d: allow the super-user to make hard links to directories, uh huh

[Dan Jacobson]

$ info ln
`-d'
`-F'
`--directory'
     Allow the super-user to make hard links to directories.
$ ln --help
  -d, -F, --directory         hard link directories (super-user only)
$ man ln
       -d, -F, --directory
              hard link directories (super-user only)

Oh great, one spends hours tying to find what is wrong only to
discover,
$ info ln
On all existing implementations, you cannot make a hard link to a
directory, and hard links cannot cross filesystem boundaries.  (These
restrictions are not mandated by POSIX, however.)

Therefore, kindly say everywhere you say super-user only,
instead say "few systems, super-user only".