update docstring to clarify usage of -c option

tools/editconf.py

@@ -14,6 +14,8 @@
 #
 # NAME VALUE
 #
+# If the -c option is given, then the supplied character becomes the comment character
+#
 # If the -w option is given, then setting lines continue onto following
 # lines while the lines start with whitespace, e.g.:
 #
@@ -24,7 +26,7 @@ import sys, re
 
 # sanity check
 if len(sys.argv) < 3:
-	print("usage: python3 editconf.py /etc/file.conf [-s] [-w] [-t] NAME=VAL [NAME=VAL ...]")
+	print("usage: python3 editconf.py /etc/file.conf [-s] [-w] [-c <CHARACTER>] [-t] NAME=VAL [NAME=VAL ...]")
 	sys.exit(1)
 
 # parse command line arguments