diff -r 156bfa6a2836 -r f13390b2c1ee src/Tools/Demo/etc/options
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Tools/Demo/etc/options	Sat Nov 25 16:13:08 2023 +0100
@@ -0,0 +1,6 @@
+(* :mode=isabelle-options: *)
+
+section "Demo"
+
+option demo_prefix : string = ""
+  -- "line prefix for output of arguments"