Makefile: use git-describe to mark the git version.

Note: with this commit, the GIT maintainer workflow must change.
GIT-VERSION-GEN is now the file to munge when the default
version needs to be changed, not Makefile.  The tag needs to be
pushed into the repository to build the official tarball and
binary package beforehand.

Signed-off-by: Junio C Hamano <junkio@cox.net>

.gitignore

@@ -1,3 +1,4 @@
+GIT-VERSION-FILE
 git
 git-add
 git-am

GIT-VERSION-GEN

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+GVF=GIT-VERSION-FILE
+
+VN=$(git describe --abbrev=4 HEAD 2>/dev/null) || VN=v1.0.GIT
+VN=$(expr "$VN" : v'\(.*\)')
+if test -r $GVF
+then
+	VC=$(sed -e 's/^GIT_VERSION = //' <$GVF)
+else
+	VC=unset
+fi
+test "$VN" = "$VC" || {
+	echo >&2 "GIT_VERSION = $VN"
+	echo "GIT_VERSION = $VN" >$GVF
+}
+
+

Makefile

@@ -55,7 +55,9 @@ all:
 # Define USE_STDEV below if you want git to care about the underlying device
 # change being considered an inode change from the update-cache perspective.
 
-GIT_VERSION = 1.0.GIT
+GIT-VERSION-FILE: .FORCE-GIT-VERSION-FILE
+	@sh ./GIT-VERSION-GEN
+-include GIT-VERSION-FILE
 
 # CFLAGS and LDFLAGS are for the users to override from the command line.
 
@@ -369,7 +371,7 @@ all: $(ALL_PROGRAMS)
 all:
 	$(MAKE) -C templates
 
-git$X: git.c $(LIB_FILE) Makefile
+git$X: git.c $(LIB_FILE)
 	$(CC) -DGIT_EXEC_PATH='"$(bindir)"' -DGIT_VERSION='"$(GIT_VERSION)"' \
 		$(CFLAGS) $(COMPAT_CFLAGS) -o $@ $(filter %.c,$^) $(LIB_FILE)
 
@@ -398,8 +400,12 @@ $(patsubst %.py,%,$(SCRIPT_PYTHON)) : % : %.py
 git-cherry-pick: git-revert
 	cp $< $@
 
-# format-patch records GIT_VERSION
-git-format-patch: Makefile
+# These can record GIT_VERSION
+git$X git.spec \
+	$(patsubst %.sh,%,$(SCRIPT_SH)) \
+	$(patsubst %.perl,%,$(SCRIPT_PERL)) \
+	$(patsubst %.py,%,$(SCRIPT_PYTHON)) \
+	: GIT-VERSION-FILE
 
 %.o: %.c
 	$(CC) -o $*.o -c $(ALL_CFLAGS) $<
@@ -475,7 +481,7 @@ install-doc:
 
 ### Maintainer's dist rules
 
-git.spec: git.spec.in Makefile
+git.spec: git.spec.in
 	sed -e 's/@@VERSION@@/$(GIT_VERSION)/g' < $< > $@
 
 GIT_TARNAME=git-$(GIT_VERSION)
@@ -510,4 +516,8 @@ clean:
 	$(MAKE) -C Documentation/ clean
 	$(MAKE) -C templates clean
 	$(MAKE) -C t/ clean
+	rm -f GIT-VERSION-FILE
+
+.PHONY: all install clean
+.PHONY: .FORCE-GIT-VERSION-FILE