[tz] Undoing the effect of the new alike-since-1970 patch

[Derick Rethans]

Hi Paul,

I welcome the direction that this is going in, but I've some 
observations:

On Fri, 4 Jun 2021, Paul Eggert via tz wrote:

> There's been a clear need expressed to support tzdb users who would 
> rather not deal with the effects of the recently-proposed 
> alike-since-1970 patch. On the other hand there are also fairness and 
> guideline-oriented reasons for the patch, which was originally 
> discussed and installed with more than our usual care and review.

Wrt to "fairness". Although IMO it is sad to see that some tzids don't 
have pre-1970 data, I don't think you can call it "fair" to then 
remove/restrict/hide away this data for tzids which have this data. 
"If I can't have it, you can't have it" is fairly infantile, IMO.

>From what I remember, the policy/guideline has always just been "don't 
split up zones for only pre-1970 data", without any mentions of hiding 
the data that we already have behind a flag.

> Because of the extensive followup discussions I don't see how a single 
> version could be appealing to both sides of this disagreement.
> 
> So I propose we add a Makefile or similar build-time option to let 
> tzdb users have it either way. Set the flag one way, and it will be as 
> if the recently-proposed changes did not occur. Set it the other way, 
> and you'll get the changes.

Who was actively asking for the data to be restricted? I might have 
missed it when going through the whole thread, but I don't think there 
was anybody (besides yourself) actively asking for this to happen.

If there was nobody actively asking for the pre-1970 to be hidden for 
some zones, does it really make sense to add such a new flag, especially 
considering it will add more work for the TZ Coordinator?

If current users don't care about pre-1970 data, then can already invoke 
zic with "zic -r @0" as is documented in zic(8).

> If there is support for this idea, I expect to be able to implement 
> this option soon, in plenty of time before any urgent change due to a 
> real-world rule change arrives.

As Stephen said, I would prefer that the current state to be reversed 
first, and then we can discuss what we want in the other thread that 
Stephen started.

cheers,
Derick
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