From b33336be5186c9b439c19f4125e28ab6ec77332a Mon Sep 17 00:00:00 2001
From: Maxim Belkin <maxim.belkin@gmail.com>
Date: Thu, 24 Jun 2021 03:33:52 -0500
Subject: [PATCH] Makefile: require index.md (#607)

---
 Makefile | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 8b02ab11..2068f87a 100644
--- a/Makefile
+++ b/Makefile
@@ -41,11 +41,11 @@ endif
 .PHONY: site docker-serve repo-check clean clean-rmd
 
 ## * serve            : render website and run a local server
-serve : lesson-md
+serve : lesson-md index.md
 	${JEKYLL} serve
 
 ## * site             : build website but do not run a server
-site : lesson-md
+site : lesson-md index.md
 	${JEKYLL} build
 
 ## * docker-serve     : use Docker to serve the site
@@ -172,3 +172,10 @@ ifeq (, $(PYTHON))
 else
 	@:
 endif
+
+index.md :
+ifeq (, $(wildcard index.md))
+	$(error index.md not found)
+else
+	@:
+endif