[set-default-theme] Call usage function in --help

This way the top line of the help output gives usage.

diff --git a/scripts/plymouth-set-default-theme.in b/scripts/plymouth-set-default-theme.in
index 195940dfd3481c626d33f27617f30dc2b342d1bd..1929f00d88199962f140ca30d79628ca818357e6 100755 (executable)
--- a/scripts/plymouth-set-default-theme.in
+++ b/scripts/plymouth-set-default-theme.in
@@ -22,7 +22,7 @@ function usage ()
 function show_help() {
   cat <<EOF
 
-    ${0##*/} [opt]
+    $(usage)
 
      --help             show this help message
      --list             show available themes