ls: Improve description of --group-directories-first.

* src/ls.c (usage) [--group-directories-first]: Improve description.
* doc/coreutils.texi (Which files are listed): Likewise.

1 files changed, 2 insertions, 0 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 23d0ab45b..016673a3b 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -5894,6 +5894,8 @@ directories and the files separately using the selected sort key
 (see --sort option).
 That is, this option specifies a primary sort key,
 and the --sort option specifies a secondary key.
+However, any use of @option{--sort=none}
+(@option{-U}) disables this option altogether.
 
 @item --hide=PATTERN
 @opindex --hide=@var{pattern}