mingw: Use the Git wrapper for builtins

This reduces the disk footprint of a full Git for Windows setup
dramatically because on Windows, one cannot assume that hard links are
supported.

The net savings are calculated easily: the 32-bit `git.exe` file weighs
in with 7662 kB while the `git-wrapper.exe` file (modified to serve as a
drop-in replacement for builtins) weighs a scant 21 kB. At this point,
there are 109 builtins which results in a total of 813 MB disk space
being freed up by this commit.

Yes, that is really more than half a gigabyte.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

Makefile

@@ -1672,11 +1672,17 @@ version.sp version.s version.o: EXTRA_CPPFLAGS = \
 	'-DGIT_VERSION="$(GIT_VERSION)"' \
 	'-DGIT_USER_AGENT=$(GIT_USER_AGENT_CQ_SQ)'
 
+ifeq (,$(BUILT_IN_WRAPPER))
 $(BUILT_INS): git$X
 	$(QUIET_BUILT_IN)$(RM) $@ && \
 	ln $< $@ 2>/dev/null || \
 	ln -s $< $@ 2>/dev/null || \
 	cp $< $@
+else
+$(BUILT_INS): $(BUILT_IN_WRAPPER)
+	$(QUIET_BUILT_IN)$(RM) $@ && \
+	cp $< $@
+endif
 
 common-cmds.h: ./generate-cmdlist.sh command-list.txt
 
@@ -2239,6 +2245,24 @@ profile-install: profile
 profile-fast-install: profile-fast
 	$(MAKE) install
 
+ifeq (,$(BUILT_IN_WRAPPER))
+LN_OR_CP_BUILT_IN_BINDIR = \
+	test -z "$(NO_INSTALL_HARDLINKS)" && \
+	ln "$$bindir/git$X" "$$bindir/$$p" 2>/dev/null || \
+	ln -s "git$X" "$$bindir/$$p" 2>/dev/null || \
+	cp "$$bindir/git$X" "$$bindir/$$p" || exit;
+LN_OR_CP_BUILT_IN_EXECDIR = \
+	test -z "$(NO_INSTALL_HARDLINKS)" && \
+	ln "$$exectir/git$X" "$$exectir/$$p" 2>/dev/null || \
+	ln -s "git$X" "$$exectir/$$p" 2>/dev/null || \
+	cp "$$exectir/git$X" "$$exectir/$$p" || exit;
+else
+LN_OR_CP_BUILT_IN_BINDIR = \
+	cp "$(BUILT_IN_WRAPPER)" "$$bindir/$$p" || exit;
+LN_OR_CP_BUILT_IN_EXECDIR = \
+	cp "$(BUILT_IN_WRAPPER)" "$$execdir/$$p" || exit;
+endif
+
 install: all
 	$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(bindir_SQ)'
 	$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(gitexec_instdir_SQ)'
@@ -2277,17 +2301,11 @@ endif
 	} && \
 	for p in $(filter $(install_bindir_programs),$(BUILT_INS)); do \
 		$(RM) "$$bindir/$$p" && \
-		test -z "$(NO_INSTALL_HARDLINKS)" && \
-		ln "$$bindir/git$X" "$$bindir/$$p" 2>/dev/null || \
-		ln -s "git$X" "$$bindir/$$p" 2>/dev/null || \
-		cp "$$bindir/git$X" "$$bindir/$$p" || exit; \
+		$(LN_OR_CP_BUILT_IN_BINDIR) \
 	done && \
 	for p in $(BUILT_INS); do \
 		$(RM) "$$execdir/$$p" && \
-		test -z "$(NO_INSTALL_HARDLINKS)" && \
-		ln "$$execdir/git$X" "$$execdir/$$p" 2>/dev/null || \
-		ln -s "git$X" "$$execdir/$$p" 2>/dev/null || \
-		cp "$$execdir/git$X" "$$execdir/$$p" || exit; \
+		$(LN_OR_CP_BUILT_IN_EXECDIR) \
 	done && \
 	remote_curl_aliases="$(REMOTE_CURL_ALIASES)" && \
 	for p in $$remote_curl_aliases; do \

config.mak.uname

@@ -525,6 +525,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	X = .exe
 	SPARSE_FLAGS = -Wno-one-bit-signed-bitfield
 	OTHER_PROGRAMS += git-wrapper$(X)
+	BUILT_IN_WRAPPER = git-wrapper$(X)
 ifneq (,$(wildcard ../THIS_IS_MSYSGIT))
 	htmldir = share/doc/git/$(firstword $(subst -, ,$(GIT_VERSION)))/html
 	prefix =