shell-scripts usage(): consistently exit with non-zero

Earlier conversion of shell scripts to parse-options made usage()
to run "git cmd -h" which in turn emit LONG_USAGE and exit with 0
status.  This is inconsistent with the scripts that do not use
parse-options, whose usage() died with the message, exiting with 1.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-sh-setup.sh

@@ -18,7 +18,8 @@ die() {
 
 if test -n "$OPTIONS_SPEC"; then
 	usage() {
-		exec "$0" -h
+		"$0" -h
+		exit 1
 	}
 
 	parseopt_extra=