Merge branch 'ab/make-sparse-for-real'

Prevent "make sparse" from running for the source files that
haven't been modified.

* ab/make-sparse-for-real:
  Makefile: make the "sparse" target non-.PHONY

.gitignore

@@ -225,6 +225,7 @@
 *.lib
 *.res
 *.sln
+*.sp
 *.suo
 *.ncb
 *.vcproj

Makefile

@@ -2903,11 +2903,13 @@ check-sha1:: t/helper/test-tool$X
 
 SP_OBJ = $(patsubst %.o,%.sp,$(C_OBJ))
 
-$(SP_OBJ): %.sp: %.c GIT-CFLAGS FORCE
+$(SP_OBJ): %.sp: %.c %.o GIT-CFLAGS
 	$(QUIET_SP)cgcc -no-compile $(ALL_CFLAGS) $(EXTRA_CPPFLAGS) \
-		$(SPARSE_FLAGS) $(SP_EXTRA_FLAGS) $<
+		-Wsparse-error \
+		$(SPARSE_FLAGS) $(SP_EXTRA_FLAGS) $< && \
+	>$@
 
-.PHONY: sparse $(SP_OBJ)
+.PHONY: sparse
 sparse: $(SP_OBJ)
 
 EXCEPT_HDRS := $(GENERATED_H) unicode-width.h compat/% xdiff/%
@@ -3235,6 +3237,7 @@ clean: profile-clean coverage-clean cocciclean
 	$(RM) $(ALL_PROGRAMS) $(SCRIPT_LIB) $(BUILT_INS) git$X
 	$(RM) $(TEST_PROGRAMS)
 	$(RM) $(FUZZ_PROGRAMS)
+	$(RM) $(SP_OBJ)
 	$(RM) $(HCC)
 	$(RM) -r bin-wrappers $(dep_dirs) $(compdb_dir) compile_commands.json
 	$(RM) -r po/build/