bsdinstall: separate out dist selection in prep for pkgbase support

[brd]

Summary

No functional change intended.

[jrtc27]

I've tried to give this a more thorough review and found some issues. Please test it more thoroughly for the various different cases that arise.

usr.sbin/bsdinstall/scripts/Makefile

22

Needs a corresponding OptionalObsoleteFiles.inc entry

usr.sbin/bsdinstall/scripts/auto

67

I won't object to this, but I do feel it's a bit odd to introduce this variable when =n doesn't work. Would it not be better to introduce this at the same time as you add the actual functionality for the =n case?

usr.sbin/bsdinstall/scripts/selectdists

48–53

I believe you still need this dance around it (and FD 3 isn't hooked up to anything here AFAICT)?

70

You can't do this here, it needs to be done up in auto as it checks this variable to know whether to skip netconfig. Otherwise the information is lost the moment selectdists exits.