git-commit: do not fail to print the diffstat even if there is a file named HEAD

Signed-off-by: Michael Loeffler <zvpunry@zvpunry.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-commit.sh

@@ -628,7 +628,7 @@ then
 	if test -z "$quiet"
 	then
 		echo "Created${initial_commit:+ initial} commit $commit"
-		git-diff-tree --shortstat --summary --root --no-commit-id HEAD
+		git-diff-tree --shortstat --summary --root --no-commit-id HEAD --
 	fi
 fi