commit/status -h: show usage even with broken configuration

commit/status -h: show usage even with broken configuration

"git status" and "git commit" read .git/config and .gitmodules before
parsing options, but there is no reason to access a repository at all
when the caller just wanted to know what arguments are accepted.

[jn: rewrote the log message and added test]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>