[bug#30216] [WIP v5] services: agetty: Make tty optional.

[Danny Milosavljevic]

> +(define (default-tty)  

>Could you add a docstring, like, IIUC: “Return a gexp that determines a
>reasonable default serial port to use as the tty.  This is primarily
>useful for headless systems such as ARM SoCs.”
>In the manual, for the agetty service, it would be good to document the
>‘agetty.tty’ kernel command-line option.

Sure.

> Rather use ‘linux-command-line’ from (gnu build linux-boot).
> ‘find-long-option’ in the same module does almost what you want, but if
> you really want to support repeated “agetty.tty” options, you’ll have to
> make a new ‘find-long-options’ (plural) variant.

It's more for the repeated "console=" options which Linux supports.

>Perhaps ‘default-serial-port’ is more appropriate in fact?

Yeah.