Re: [PATCH 4/5] Makefile: add USE_SHA1DC knob

Jeff King [off-list ref] writes:

+ifdef USE_SHA1DC
+	LIB_OBJS += sha1dc/sha1.o
+	LIB_OBJS += sha1dc/ubc_check.o
+	BASIC_CFLAGS += -DSHA1_SHA1DC

The name of this CPP symbol is one difference between this and
Linus's version.  Wouldn't "-DSHA1_DC" make more sense?

Another difference is that your version adds USE_SHA1DC to
GIT-BUILD-OPTIONS in patch 5/5; I thought GIT-CFLAGS forces
rebuilding and that was sufficient, but GIT-BUILD-OPTIONS is
available to tests for introspection, so adding it is needed
for that reason.