git-var: make it work in subdirectory.

Use setup_git_directory() so that it can find its .git
directory.

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

var.c

@@ -57,6 +57,8 @@ int main(int argc, char **argv)
 	if (argc != 2) {
 		usage(var_usage);
 	}
+
+	setup_git_directory();
 	setup_ident();
 	val = NULL;