Attached is a patch for help-fns.el. It modifies `describe-function' and
`describe-variable', so that a prefix arg means that candidates are commands
and user options, respectively. So `C-u C-h f' shows and accepts only
commands as completion candidates, and `C-u C-h v' shows and accepts only
user options for completion.

In addition, for convenience, two new commands are defined to do the same
thing without `C-u': `describe-command' and `describe-option'. This is
especially useful for newbies, who might search for something that describes
a command or an option.

Yes, users already have `apropos-command' and `apropos-variable' (which
should be called `apropos-option'), which give info about commands and
options, and they can get to a command or option description from there. I
nevertheless think this trivial addition is helpful, and not just for
newbies.

Caveat: I patched the latest CVS help-fns.el, but I have not tested the
patch with CVS Emacs. I have only an Emacs 22.1 binary for Windows. I have
tested a similar patch for Emacs 22.1. (`describe-variable' now uses things
such as `with-selected-frame', which are not available with Emacs 22.1.)