bug#397: 23.0.60; T in Info when in (dir)

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 27 Apr 2016 10:46:38 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 397@debbugs.gnu.org
> 
> `Info-toc' should raise an error immediately, if the current node
> is the top.  Something like this, perhaps:
> 
> (defun Info-toc ()
>   "@@@@@@@@@"
>   (interactive)
>   (when (equal Info-current-file "dir") (error "@@@@@@@@@@@@@@@@@"))

So, from now on, no Info manual can be called "dir" or "dir.info", or
suchlikes?  Does dimming an option in a rarely-used menu really
justify this?  I don't think so.

We should look for a better solution, if one exists.  If it doesn't,
then it isn't a catastrophe to have that option be available and fail
if invoked where it cannot work.  No one who knows something about
Info will invoke that function in this situation, anyway.

> But probably not.  `Info-index' does only this:
> (equal Info-current-file "dir")

Bad, bad Info-index!