Makefile: rely on GNU make; derive syntax-check rule names

Rather than requiring that each sc_ rule be listed as a dependent
of "check", use features of GNU make to derive the list.
* Makefile (syntax-check-rules): Define.
(check): Depend on the new variable, not the hard-coded list.
Add a comment listing a few requirements.

1 files changed, 9 insertions, 5 deletions

diff --git a/Makefile b/Makefile
index 9c0d0c3bf4..c9bfc1615b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,13 @@
-# Makefile for gnulib central.
+# GNU Makefile for gnulib central.
 # Copyright (C) 2006, 2009-2011 Free Software Foundation, Inc.
 #
 # Copying and distribution of this file, with or without modification,
 # in any medium, are permitted without royalty provided the copyright
 # notice and this notice are preserved.
 
+# This Makefile requires the use of GNU make.  Some targets require
+# that you have tools like git, makeinfo and cppi installed.
+
 # Produce some files that are not stored in the repository.
 all:
 
@@ -12,11 +15,12 @@ all:
 info html dvi pdf:
 	cd doc && $(MAKE) $@ && $(MAKE) mostlyclean
 
+# Collect the names of rules starting with `sc_'.
+syntax-check-rules := $(sort $(shell sed -n 's/^\(sc_[a-zA-Z0-9_-]*\):.*/\1/p'\
+			Makefile))
+
 # Perform some platform independent checks on the gnulib code.
-check: \
-  sc_prohibit_augmenting_PATH_via_TESTS_ENVIRONMENT			\
-  sc_pragma_columns							\
-  sc_prefer_ac_check_funcs_once
+check: $(syntax-check-rules)
 
 sc_prefer_ac_check_funcs_once:
 	if test -d .git; then						\