From aa7d0aec091797df7ae72edccad22d462587568a Mon Sep 17 00:00:00 2001
From: "Achim D. Brucker" <adbrucker@0x5f.org>
Date: Fri, 24 Jun 2022 18:50:32 +0100
Subject: [PATCH] Print help message, if script is invoked without prefixing
 'isabelle env'.

---
 install-afp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/install-afp b/install-afp
index 735cd7e..57da18c 100755
--- a/install-afp
+++ b/install-afp
@@ -129,6 +129,12 @@ do
     shift
 done
 
+if [ -z ${ISABELLE_TOOL+x} ];
+then
+    print_help
+    exit 1
+fi
+
 ACTUAL_ISABELLE_VERSION=`$ISABELLE_TOOL version`
 
 ISABELLE_VERSION="Isabelle$($ISABELLE_TOOL options -g dof_isabelle)"