+# subdirmk - rules for regenerating makefiles etc.
+# Copyright 2019 Mark Wooding
+# Copyright 2019 Ian Jackson
+# SPDX-License-Identifier: LGPL-2.0-or-later
+# There is NO WARRANTY.
+
+# Usage:
+# include subdirmk/regen.mk
+# (probably in toplevel Dir.sd.mk)
+#
+# Arranges that config.status is automatically rerun to update
+# makefiles from templates, whenever a template *.sd.mk or *.mk.in is
+# edited; and that autoconf is rerun if configure's inputs are edited.
+#
+# If you add includes to configure.ac, add them to CONFIGURE_ACS.
+#
+# Makefiles updated by config.status and passed to SUBDIRMK_MAKEFILES
+# in configure.ac are automatically handled too. If you have other
+# files updated by config.status (eg, the output of autoheader) you
+# need to put them in CONFIG_STATUS_OUTPUTS (before your inclusion
+# of regen.mk).
+#
+# Also provides a `realclean::' target at the toplevel which deletes
+# the autoconf output. (This is suitable for being part of a recursive
+# target creaed by setting &TARGETS_realclean in appropriate .sd.mk.)