bug#29872: 26.0.90; `man' output encoding, hyphen chars

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 31 Dec 2017 09:34:42 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 29872@debbugs.gnu.org
> 
> > For Emacs 26, I've just committed a change that introduces a new
> > defcustom, Man-coding-system, which you can customize to utf-8 to get
> > the correct behavior in your case.  For older versions of Emacs, you
> > will need to use a separate command that invokes 'man' as shown above,
> > because man.el unconditionally uses locale-coding-system for that, and
> > locale-coding-system on MS-Windows can never be UTF-8.
> 
> Thank you.  I assume that you'll mention this in NEWS.

I'm not sure it's NEWS worthy.  The situations in which this variable
is useful are quite obscure (see below) and since the code in its
present form exists for a long time without anyone complaining, we can
assume they are rare.  And mentioning this variable won't enhance its
discoverability, since no one will know to look it up when/if they
bump into this problem.

> I wonder whether it is something that I should set in
> `setup-cygwin.el' or just tell users there, in a comment,
> that they will need to customize it.

Probably the latter.

> Leavning aside, for the moments, arguments about whether
> code should mess with user options, can you say when it
> is appropriate, typically, for a Windows user to customize
> that option?

On Windows, probably only when using a Cygwin 'man' from a native
Windows Emacs.  On some other system, only if the man pages were
pre-formatted on another system with an incompatible locale setting,
or if Groff was forced to produce UTF-8 encoded man pages when those
man pages were formatted.

> Does it have to do with whether Cygwin is used, for instance (with a
> non-Cygwin Emacs)?  Or does the option default value depend on the
> platform perhaps?

On almost any platform with correct setup, the default of using
locale-coding-system for decoding the man pages should work correctly,
so the default should not depend on the platform.  This new variable
is a fire escape for those rare cases where the default doesn't work.