Merge branch 'rj/sparse-flags'

Use of the sparse tool got easier to customize from the command
line to help developers.

* rj/sparse-flags:
  Makefile: improve SPARSE_FLAGS customisation
  config.mak.uname: remove obsolete SPARSE_FLAGS setting

Makefile

@@ -574,7 +574,11 @@ SPATCH = spatch
 
 export TCL_PATH TCLTK_PATH
 
-SPARSE_FLAGS =
+# user customisation variable for 'sparse' target
+SPARSE_FLAGS ?=
+# internal/platform customisation variable for 'sparse'
+SP_EXTRA_FLAGS =
+
 SPATCH_FLAGS = --all-includes --patch .
 
 
@@ -2370,10 +2374,10 @@ gettext.sp gettext.s gettext.o: GIT-PREFIX
 gettext.sp gettext.s gettext.o: EXTRA_CPPFLAGS = \
 	-DGIT_LOCALE_PATH='"$(localedir_relative_SQ)"'
 
-http-push.sp http.sp http-walker.sp remote-curl.sp imap-send.sp: SPARSE_FLAGS += \
+http-push.sp http.sp http-walker.sp remote-curl.sp imap-send.sp: SP_EXTRA_FLAGS += \
 	-DCURL_DISABLE_TYPECHECK
 
-pack-revindex.sp: SPARSE_FLAGS += -Wno-memcpy-max-count
+pack-revindex.sp: SP_EXTRA_FLAGS += -Wno-memcpy-max-count
 
 ifdef NO_EXPAT
 http-walker.sp http-walker.s http-walker.o: EXTRA_CPPFLAGS = -DNO_EXPAT
@@ -2387,7 +2391,7 @@ endif
 ifdef USE_NED_ALLOCATOR
 compat/nedmalloc/nedmalloc.sp compat/nedmalloc/nedmalloc.o: EXTRA_CPPFLAGS = \
 	-DNDEBUG -DREPLACE_SYSTEM_ALLOCATOR
-compat/nedmalloc/nedmalloc.sp: SPARSE_FLAGS += -Wno-non-pointer-null
+compat/nedmalloc/nedmalloc.sp: SP_EXTRA_FLAGS += -Wno-non-pointer-null
 endif
 
 git-%$X: %.o GIT-LDFLAGS $(GITLIBS)
@@ -2711,7 +2715,7 @@ SP_OBJ = $(patsubst %.o,%.sp,$(C_OBJ))
 
 $(SP_OBJ): %.sp: %.c GIT-CFLAGS FORCE
 	$(QUIET_SP)cgcc -no-compile $(ALL_CFLAGS) $(EXTRA_CPPFLAGS) \
-		$(SPARSE_FLAGS) $<
+		$(SPARSE_FLAGS) $(SP_EXTRA_FLAGS) $<
 
 .PHONY: sparse $(SP_OBJ)
 sparse: $(SP_OBJ)

config.mak.uname

@@ -555,7 +555,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	RC = windres -O coff
 	NATIVE_CRLF = YesPlease
 	X = .exe
-	SPARSE_FLAGS = -Wno-one-bit-signed-bitfield
 ifneq (,$(wildcard ../THIS_IS_MSYSGIT))
 	htmldir = doc/git/html/
 	prefix =