Documentation for usual.mk.in

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/subdirmk/usual.mk.in b/subdirmk/usual.mk.in
index c40a18f22b58eb44ec03404372ff3bafe430f50c..66c71ebcde5ae968a04fa001accef3cd494800cb 100644 (file)
--- a/subdirmk/usual.mk.in
+++ b/subdirmk/usual.mk.in
@@ -3,6 +3,13 @@
 #  Copyright 2019 Ian Jackson
 # SPDX-License-Identifier: LGPL-2.0-or-later
 
+# Usage:
+#   include subdirmk/usual.mk
+# (probably in toplevel Subdir.sd.mk)
+#
+# Provides various conventional `make' variables, and a
+# rule for compiling C programs.
+
 VPATH          = $(top_srcdir)
 
 prefix         = @prefix@