This committed as part of rS321178

usual sh style puts the individual case entries aligned with case

Maybe add "Please check for a newer snapshot." -- @gjb does that sound reasonable?

My vim auto-indent script does the same indentation style as in this diff, which I tend to prefer. We do not have a hard-written style(9) for sh(1) scripts that I can find.

Yes.

But this indentation style is not consistent with the rest of bsdinstall

If for consistency in bsdinstall(8), then ok.

fwiw the no-extra-indent style is nearly universal in the src tree (in bin/usr.bin/sbin/usr.sbin)

One small improvement, we should be able to avoid the extra invocation (sed) and just use *-ALPHA*|*-CURRENT|*-STABLE|*-PRERELEASE) in the case statement.