GIT-VERSION-GEN: detect dirty tree and mark the version accordingly.

If we are building from a working tree with local modifications,
mark the version accordingly.

Deliberately uses '-' to prevent RPM from being built from such
a tree.

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

GIT-VERSION-GEN

@@ -10,6 +10,15 @@ VN=$(cat version) ||
 VN="$DEF_VER"
 
 VN=$(expr "$VN" : v*'\(.*\)')
+
+dirty=$(sh -c 'git-diff-index --name-only HEAD' 2>/dev/null) || dirty=
+case "$dirty" in
+'')
+	;;
+*)
+	VN="$VN-dirty" ;;
+esac
+
 if test -r $GVF
 then
 	VC=$(sed -e 's/^GIT_VERSION = //' <$GVF)