add coccicheck make target

Provide a simple way to run Coccinelle against all source files, in the
form of a Makefile target.  Running "make coccicheck" applies each
.cocci file in contrib/coccinelle/ on all source files.  It generates
a .patch file for each .cocci file, containing the actual changes for
effecting the transformations described by the semantic patches.

Non-empty .patch files are reported.  They can be applied to the work
tree using "patch -p0", but should be checked to e.g. make sure they
don't screw up formatting or create circular references.

Coccinelle's diagnostic output (stderr) is piped into .log files.

Linux has a much more elaborate make target of the same name; let's
start nice and easy.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -456,6 +456,7 @@ CURL_CONFIG = curl-config
 PTHREAD_LIBS = -lpthread
 PTHREAD_CFLAGS =
 GCOV = gcov
+SPATCH = spatch
 
 export TCL_PATH TCLTK_PATH
 
@@ -2296,6 +2297,18 @@ check: common-cmds.h
 		exit 1; \
 	fi
 
+C_SOURCES = $(patsubst %.o,%.c,$(C_OBJ))
+%.cocci.patch: %.cocci $(C_SOURCES)
+	@echo '    ' SPATCH $<; \
+	for f in $(C_SOURCES); do \
+		$(SPATCH) --sp-file $< $$f; \
+	done >$@ 2>$@.log; \
+	if test -s $@; \
+	then \
+		echo '    ' SPATCH result: $@; \
+	fi
+coccicheck: $(patsubst %.cocci,%.cocci.patch,$(wildcard contrib/coccinelle/*.cocci))
+
 ### Installation rules
 
 ifneq ($(filter /%,$(firstword $(template_dir))),)
@@ -2487,6 +2500,7 @@ clean: profile-clean coverage-clean
 	$(RM) -r $(GIT_TARNAME) .doc-tmp-dir
 	$(RM) $(GIT_TARNAME).tar.gz git-core_$(GIT_VERSION)-*.tar.gz
 	$(RM) $(htmldocs).tar.gz $(manpages).tar.gz
+	$(RM) contrib/coccinelle/*.cocci.patch*
 	$(MAKE) -C Documentation/ clean
 ifndef NO_PERL
 	$(MAKE) -C gitweb clean