ostree-deploy: /etc/fstab is only created during deploy, not possible in repo

When using the ostree-deploy, I find that /etc/fstab is created inside the
    <ostree-deploy-dir>/etc/fstab

Therefore, the `/usr/etc/fstab` in the repo is empty.

I'd like to have the /etc/fstab generated early, so that I can commit it to 
the OSTree's repo first.

My requirement is to have the factory setting restore function, 
which I  can revert the /etc/ changes by replace it with /usr/etc/.