[tz] Add option to act like global-tz

[Robert Elz]

    Date:        Mon, 15 Aug 2022 13:24:48 -0700
    From:        Paul Eggert <eggert at cs.ucla.edu>
    Message-ID:  <fb33ecdc-753d-ea7e-6d4d-f30af7b0e059 at cs.ucla.edu>

  | In what sense is that not true for the tarball format in question[1]?

The data isn't in the files it belongs in.

  | What programs go awry if that tarball's data are used, and what are the 
  | symptoms of these failures?

One cannot easily checked what has changed, as the whole data file
(all of them in that format) has gone away.    I know you understand
version control systems - we use one as well (currently cvs, gradually
migrating to mercurial) and being able to look and see what changed in
what version (and why) is important.

  | If the main problem is that a user who wants to hand-edit this data will 
  | not know to edit 'etcetera' rather than (say) 'australasia', then it'd 
  | be easy to change the tarball generator so that instead of 'australasia' 
  | being empty it would contain a comment like "# Please edit the file 
  | 'etcetera' instead."; would that help?

No.   If you would put the data which belongs in australasia back in the
australasia file, that would help (and the same with all the others).
Even if the file had markers in it, showing which parts belong to (or
originate from if you prefer) which original file it would be better.
That is, assuming that when the backzone data is merged in, it is put
into the correct places in the file (that from which it was removed)
so that we don't have countless differences which are in reality simply
lines moving around.

  | [1] Here's the latest iteration of the tarball format in question:
  | https://www.cs.ucla.edu/~eggert/tz/tzdata2022b-5-gc9ba895-tailored.tar.gz

Thanks -- in later reading of previously unread messages, I saw there was
one of those for 2022a as well, had I seen that one I might have looked at
it earlier, not that I think that would have changed anything.

This file (as it doesn't include anything from backzone) doesn't help at
all though - the tzdata file as distributed is easier to deal with than
that particular one - but I assume that much is able to be altered.

kre