bug#41250: 28.0.50; Dired displays unconditionally ls-switches on modeline

[Eli Zaretskii]

> From: Arthur Miller <arthur.miller@live.com>
> Cc: drew.adams@oracle.com,  41250@debbugs.gnu.org,  juri@linkov.net
> Date: Mon, 18 May 2020 00:57:42 +0200
> 
> Another question: can I assume, at this time of civilisation
> development, that everybody has GNU ls, since binutils, or coreutils, or
> what is the name, is probably default on most *nix distros, as well as
> on msys2 which is needed to build on Windows. No idea how Mac people are
> doing in that regard though?

No, we cannot assume GNU 'ls', since both *BSD Unix systems and macOS
(which is BSD-ish) use non-GNU 'ls'.

> I can try to detect if gnu ls is present say when dired-mode is
> loaded, but that would slow down dired every time we open a directory.

Don't we already detect GNU 'ls' by looking at the //DIRED signature?
Look in files.el.