bug#34513: display-line-numbers in term mode

[Eli Zaretskii]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Cc: spacibba@aol.com, 34513@debbugs.gnu.org
> Date: Wed, 27 Feb 2019 12:21:26 -0500
> 
> >> How 'bout display-line-numbers-width or display-line-numbers-current-width?
> > I think I considered those at the time, but found them not descriptive
> > enough.
> 
> And how 'bout now?

Same.

My problem was, and is, that the name should include "display-width",
since that's what the function provides.  And the problem, of course,
is that "display-line-numbers-" already includes "display" and
"line-number", so repeating any of that produces problematic names.

> At first, TAB completion gave me the impression that there was simply no
> way to know from Elisp the actual width, because the list of completions
> seemed long enough to have the appearance of exhaustiveness.

Maybe just mentioning the variable in the doc string of
display-line-numbers-mode would be "good enough".