Record which tree the patch applies to.

Also note which version of GIT produced the patch.

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

git-format-patch.sh

@@ -212,7 +212,10 @@ Date: '"$ad"
 	echo
 	git-diff-tree -p $diff_opts "$commit" | git-apply --stat --summary
 	echo
+	git-cat-file commit "$commit^" | sed -e 's/^tree /applies-to: /' -e q
 	git-diff-tree -p $diff_opts "$commit"
+	echo "---"
+	echo "@@GIT_VERSION@@"
 
 	case "$mbox" in
 	t)