Allow installation preset from file for void-installer

Hi! I have not found discussion feature in this repo so I decided to share my thoughts in this ticket

I am trying to help void Linux devs to automate testing of void-Linux installer and thus the process of bootstrapping of new versions of void Linux from the scratch.

( already informally discussed with @classabbyamp via irc in voidlinux channel )

I see the process like that:

• get a bootable iso ( which is tested )
• kick off qemu vm bootable from the iso
• automate installation via void-installer ( this is where we have a problem )
• shut vm
• start qemu vm without bootable iso
• check that configuration is ok ( like partitioning is ok, locale is set, user account is set, etc )
• optionally runs additional tests like installing packages, configure services, etc ( more like end to end testing )
• last two steps are carried out over ssh

So the only hurdle I see here is void-installer ncurse app is hard to automate , there is way to use tmux , send-keys but it feels clunky and hard to maintain

What if we can allow to have a void-installer configuration preset stored in plain file, so void-installer could run unattended way ?

It would allow us automate many testing scenarios which could be beneficial to void Linux testing …

Start by tracing the void-installer ncurses flow and how QEMU-based installation is currently automated. Define the plain-file preset format and unattended behavior, then validate the proposal against the bootable ISO, shutdown, reboot, and SSH checks described in the issue.