l10n: Update Simplified Chinese translation

Translate new messages for git master branch.

 - sha1_name.c: 4 new messages.
 - builtin/push.c: 3 new messages.
 - git-submodule.sh: variable name changed from '$path' to '$sm_path'.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>