config: fix suggestion for failed set of multi-valued option

The command "git config set <name> <value>" fails for an option that has
multiple values.  List the "git config set" flags that can be used,
instead of old-style "git config" actions.

Reported-by: Paul Wintz <pwintz@ucsc.edu>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/config.c

diff --git a/builtin/config.c b/builtin/config.c
index 59fb113..ef1c1a9 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -974,7 +974,7 @@ static int cmd_config_set(int argc, const char **argv, const char *prefix,
 						     argv[0], comment, value);
 		if (ret == CONFIG_NOTHING_SET)
 			error(_("cannot overwrite multiple values with a single value\n"
-			"       Use a regexp, --add or --replace-all to change %s."), argv[0]);
+			"       Use --value=<pattern>, --append or --all to change %s."), argv[0]);
 	}
 
 	location_options_release(&location_opts);