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, 3 insertions, 1 deletions

diff --git a/src/ls.c b/src/ls.c
index b6dcaacaa..ff49278c7 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -4350,7 +4350,9 @@ Mandatory arguments to long options are mandatory for short options too.\n\
 "), stdout);
       fputs (_("\
       --group-directories-first\n\
-                             group directories before files\n\
+                             group directories before files.\n\
+                               augment with a --sort option, but any\n\
+                               use of --sort=none (-U) disables grouping\n\
 "), stdout);
       fputs (_("\
   -G, --no-group             in a long listing, don't print group names\n\