bug#39979: 28.0.50; `mouse-wheel-tilt-scroll' docstring is unclear/incomplete

[Göktuğ Kayaalp]

The docstring for the mentioned variable is unclear in that it does not
really tell what kind of scrolling (horizontal) is enabled and
incomplete because setting it enables horizontal scrolling and that’s
not mentioned (or, maybe tilt scrolling means that but that’s probably
an obscure term for many).

A patch is attached which is proposed as a tentative improvement. If
it’s good enough to apply, I do have my copyright assingment paperwork
done so it can be committed right away.

>From b9cf4c16d48e8b5b28748481d6649a31d92df1bd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C4=B0=2E=20G=C3=B6ktu=C4=9F=20Kayaalp?= <self@gkayaalp.com>
Date: Sun, 8 Mar 2020 00:15:01 +0300
Subject: [PATCH] * lisp/mwheel.el (mouse-wheel-tilt-scroll): improve docstring

---
 lisp/mwheel.el | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/mwheel.el b/lisp/mwheel.el
index 56150c803f..9264af1214 100644
--- a/lisp/mwheel.el
+++ b/lisp/mwheel.el
@@ -145,7 +145,8 @@ mouse-wheel-follow-mouse
 ;;; For tilt-scroll
 ;;;
 (defcustom mouse-wheel-tilt-scroll nil
-  "Enable scroll using tilting mouse wheel."
+  "Enable horizontal scrolling via mouse or touchpad. Also see
+  ‘mouse-wheel-flip-direction’."
   :group 'mouse
   :type 'boolean
   :version "26.1")
-- 
2.20.1