Add help information to invid-conv.

invid-conv

@@ -25,6 +25,16 @@
 YT_URL="$1"
 INVID_BASE="${INVID_BASE:-https://inv.nadeko.net}"
 
+if [ $# -ne 1 ]
+then
+	>&2 echo "Usage: $0 <url>"
+	exit 1
+elif [ "$1" = "-h" ]
+then
+	echo "Usage: $0 <url>"
+	exit 0
+fi
+
 if [[ $YT_URL == *"youtu.be"* ]]
 then
 	INVID_URL="${INVID_BASE}/watch?v=${YT_URL##*/}"