[tz] Add option to act like global-tz

[Robert Elz]

    Date:        Thu, 4 Aug 2022 22:54:45 +0100
    From:        Stephen Colebourne via tz <tz at iana.org>
    Message-ID:  <CACzrW9A2PPmUz8A1=mkRCGwny-oA=Kjd=dTLjweE=X0+_-Umqw at mail.gmail.com>

  | I'd recommend anyone else that wishes to use a global-tz like
  | non-merged set of data to try the new tar.gz file to see if it meets
  | their needs.

I have, while preparing to incorporate the update into NetBSD, and
it doesn't seem to (unless I am missing something) do what we need
at all.

Generating the appropriate TZIf files is only half the battle - NetBSD
users mostly have the sources (for everything) (as contracted with
Linux, etc, where even though the sources are available, a very small
fraction of users seem to make any use of that).

What I need is for the data to be in the files it has always been in.
Whether it gets there by simply unpacking the tzdata tar file, or by
running some script upon what is there to produce the desired results
is not important - but running a script to produce some other file,
which isn't one where the user would expect to find data should they
wish to change it, isn't useful to us at all.

I would have also thought that keeping all of the relevant data in
the appropriate files would make maintenance easier - when changes are
being made, all the (likely) zones that might be affected are in one
place - if you want to ignore some of them and make them links (essentially
replacing data which has been characterised as possibly, or even probably,
incorrect, with data which is almost guaranteed incorrect) then doing that
as the data is processed seems like the better choice, rather than having to
go check some other file, and make sure that everywhere that links have been
made are still appropriate to remain links seems like the hard way to me.

So, if you don't make a 2022btgz version available, I guess I will go back
to manually inserting the updates, as I have done previously.

kre

eg: since we haven't yet released a NetBSD update for 2022b, any users in
Chile who want to be prepared can easily make the update themselves, but
they need to get the same results when they do "zic southamerica" (other
than the change they made) as the TZif files that are distributed with the
system.   (And the same for europe, australasia, northamerica, africa, ...)