[PATCH v4 04/12] Makefile: have "coccicheck" re-run if flags change

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Fix an issue with the "coccicheck" family of rules that's been here
since 63f0a758a06 (add coccicheck make target, 2016-09-15), unlike
e.g. "make grep.o" we wouldn't re-run it when $(SPATCH) or
$(SPATCH_FLAGS) changed. To test new flags we needed to first do a
"make cocciclean".

This now uses the same (copy/pasted) pattern as other "DEFINES"
rules. As a result we'll re-run properly. This can be demonstrated
e.g. on the issue noted in [1]:

	$ make contrib/coccinelle/xcalloc.cocci.patch COCCI_SOURCES=promisor-remote.c V=1
	[...]
	    SPATCH contrib/coccinelle/xcalloc.cocci
	$ make contrib/coccinelle/xcalloc.cocci.patch COCCI_SOURCES=promisor-remote.c SPATCH_FLAGS="--all-includes --recursive-includes"
	    * new spatch flags
	    SPATCH contrib/coccinelle/xcalloc.cocci
	     SPATCH result: contrib/coccinelle/xcalloc.cocci.patch
	$

1. https://lore.kernel.org/git/20220823095602.GC1735@szeder.dev/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 .gitignore |  1 +
 Makefile   | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/.gitignore b/.gitignore
index 62720c6135d..7cce39270d4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@
 /GIT-PERL-HEADER
 /GIT-PYTHON-VARS
 /GIT-SCRIPT-DEFINES
+/GIT-SPATCH-DEFINES
 /GIT-USER-AGENT
 /GIT-VERSION-FILE
 /bin-wrappers/
diff --git a/Makefile b/Makefile
index b638a548182..7d4518653ce 100644
--- a/Makefile
+++ b/Makefile
@@ -1305,6 +1305,18 @@ SANITIZE_ADDRESS =
 SPATCH_FLAGS = --all-includes
 SPATCH_BATCH_SIZE = 1
 
+# Rebuild 'coccicheck' if $(SPATCH), its flags etc. change
+TRACK_SPATCH_DEFINES =
+TRACK_SPATCH_DEFINES += $(SPATCH)
+TRACK_SPATCH_DEFINES += $(SPATCH_FLAGS)
+TRACK_SPATCH_DEFINES += $(SPATCH_BATCH_SIZE)
+GIT-SPATCH-DEFINES: FORCE
+	@FLAGS='$(TRACK_SPATCH_DEFINES)'; \
+	    if test x"$$FLAGS" != x"`cat GIT-SPATCH-DEFINES 2>/dev/null`" ; then \
+		echo >&2 "    * new spatch flags"; \
+		echo "$$FLAGS" >GIT-SPATCH-DEFINES; \
+            fi
+
 include config.mak.uname
 -include config.mak.autogen
 -include config.mak
@@ -3152,6 +3164,7 @@ COCCICHECK_PATCHES_PENDING = $(COCCICHECK_PENDING:%=%.patch)
 COCCI_TEST_RES = $(wildcard contrib/coccinelle/tests/*.res)
 
 COCCI_PATCHES = $(COCCI_RULES:%=%.patch)
+$(COCCI_PATCHES): GIT-SPATCH-DEFINES
 $(COCCI_PATCHES): $(COCCI_SOURCES)
 $(COCCI_PATCHES): %.patch: %
 	$(QUIET_SPATCH) \
@@ -3175,6 +3188,7 @@ $(COCCI_PATCHES): %.patch: %
 	fi
 
 COCCI_TEST_RES_GEN = $(addprefix .build/,$(COCCI_TEST_RES))
+$(COCCI_TEST_RES_GEN): GIT-SPATCH-DEFINES
 $(COCCI_TEST_RES_GEN): .build/%.res : %.c
 $(COCCI_TEST_RES_GEN): .build/%.res : %.res
 $(COCCI_TEST_RES_GEN): .build/contrib/coccinelle/tests/%.res : contrib/coccinelle/%.cocci
@@ -3461,6 +3475,7 @@ profile-clean:
 	$(RM) $(addsuffix *.gcno,$(addprefix $(PROFILE_DIR)/, $(object_dirs)))
 
 cocciclean:
+	$(RM) GIT-SPATCH-DEFINES
 	$(RM) -r .build/contrib/coccinelle
 	$(RM) contrib/coccinelle/*.cocci.patch*
 
-- 
2.38.0.1251.g3eefdfb5e7a