bug#46979: Allow setting Man-default-entry via Local Variables

[Eli Zaretskii]

> From: Daniel Martín <mardani29@yahoo.es>
> Cc: 46979@debbugs.gnu.org,  jidanni@jidanni.org
> Date: Mon, 08 Mar 2021 20:01:31 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >
> > The need to add local variables to files is in itself a downside.
> 
> I'm not too sold on the local variables approach, either.  Perhaps we
> could expose a customization point in the form of an alist of filename
> patterns vs corresponding manuals.  Emacs would provide a few of them
> and users could expand the list with more if
> needed. `Man-default-man-entry' would consult this alist first and
> fallback to the current behavior of guessing based on the text near
> point.

That'd be better, IMO.

We could also define a trivial major mode for those files, and then
make Man-default-man-entry sensitive to that.