Re: [PATCH] strbuf: let strbuf_addftime handle %z and %Z itself

[Junio C Hamano <gitster@pobox.com>]

René Scharfe <l.s.r@web.de> writes:

> Am 07.06.2017 um 10:17 schrieb Jeff King:
>> On Sat, Jun 03, 2017 at 12:40:34PM +0200, René Scharfe wrote:
>>> Duplicates strbuf_expand to a certain extent, but not too badly, I
>>> think.  Leaves the door open for letting strftime handle the local
>>> case.
>>
>> I guess you'd plan to do that like this in the caller:
>>
>>    if (date->local)
>> 	tz_name = NULL;
>>    else
>> 	tz_name = "";
>>
>> and then your strftime() doesn't do any %z expansion when tz_name is
>> NULL.
>
> Yes, or you could look up a time zone name somewhere else -- except we
> don't have a way to do that, at least for now.

Is that only "for now"?  I have a feeling that it is fundamentally
impossible with the data we record.  When GMTOFF 9:00 is the only
thing we have for a timestamp, can we tell if we should label it as
JST (aka Asia/Tokyo) or KST (aka Asia/Seoul)?