Simple GRUB script to make grub skip it's menu if you aren't holding shift.

The script is mostly made up of bit canibalized from Ubuntu's os_prober script.

Copy 31_hold_shift to /etc/grub.d/.

For the master branch, that's all that needs to be done.

For the branch optional, you'll need to add GRUB_FORCE_HIDDEN_MENU="true" to /etc/default/grub and re-run grub-mkconfig (generally, grub-mkconfig -o /boot/grub/grub.cfg or sudo update-grub, though this may vary depending on your distribution. Consult your distributions manual if in doubt).

The latter branch has been designed to be integrated into upstream, or distribution packages without altering the default grub behaviour.