From: Ulrich Mueller <ulm@gentoo.org>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: "Junio C Hamano" <gitster@pobox.com>,
"René Scharfe" <l.s.r@web.de>, "Jeff King" <peff@peff.net>,
"Git Mailing List" <git@vger.kernel.org>
Subject: Re: [PATCH] strbuf: let strbuf_addftime handle %z and %Z itself
Date: Mon, 12 Jun 2017 18:56:34 +0200 [thread overview]
Message-ID: <22846.51138.555606.729612@a1i15.kph.uni-mainz.de> (raw)
In-Reply-To: <CACBZZX5ofJC70S09rfL_EMK2KWAoPCMun1eisi+CXeX=FSwy6Q@mail.gmail.com>
>>>>> On Mon, 12 Jun 2017, Ævar Arnfjörð Bjarmason wrote:
> On Mon, Jun 12, 2017 at 5:12 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> René Scharfe <l.s.r@web.de> writes:
>>> 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)?
> It's obviously not perfect for all the reasons mentioned in this
> thread, but we already have a timezone->offset mapping in the
> timezone_names variable in date.c, a good enough solution might be to
> simply reverse that lookup when formatting %Z
That cannot work, because there is no unique mapping from offset to
timezone name. For a given offset there may be several timezone names,
or no name at all. (For example, if I decide to commit with my local
mean time which has an offset of +0033 then there won't be any
timezone name at all.)
> Of course we can never know if you were in Tokyo or Seul from the info
> in the commit object, but we don't need to, it's enough that we just
> emit JST for +0900 and anyone reading the output has at least some
> idea what +0900 maps to.
Please don't. Outputting invented information for something that
really isn't in the data is worse than outputting no information at
all.
> We could also simply replace "%Z" with the empty string, as the the
> POSIX strftime() documentation allows for:
> http://pubs.opengroup.org/onlinepubs/009695399/functions/strftime.html
> ("Replaced by the timezone name or abbreviation, or by no bytes if no
> timezone information exists.").
IMHO the two viable possibilities are the empty string, or the same
information as for %z. But this has been said before in this thread.
tzdata2017b has the following data in its "etcetera" file, the last
column being the timezone name:
Zone Etc/GMT 0 - GMT
Zone Etc/GMT-14 14 - +14
Zone Etc/GMT-13 13 - +13
[...]
Zone Etc/GMT+12 -12 - -12
This would be at least some rationale for converting %Z to [+-]hhmm,
i.e., the same as for %z. (One could even think about [+-]hh if the
minutes part is zero, but this already looks like over-engineering
to me.)
Ulrich
next prev parent reply other threads:[~2017-06-12 16:56 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-26 18:33 git-2.13.0: log --date=format:%z not working Ulrich Mueller
2017-05-27 16:57 ` Ævar Arnfjörð Bjarmason
2017-05-27 21:46 ` Jeff King
2017-05-28 10:29 ` Ævar Arnfjörð Bjarmason
2017-05-29 0:53 ` Junio C Hamano
2017-05-28 11:43 ` René Scharfe
2017-06-02 2:23 ` Junio C Hamano
2017-06-02 3:08 ` Jeff King
2017-06-02 17:25 ` René Scharfe
2017-06-02 18:35 ` Jeff King
2017-06-02 22:04 ` Ulrich Mueller
2017-06-02 22:30 ` Jeff King
2017-06-02 22:47 ` Ulrich Mueller
2017-06-02 22:51 ` Jeff King
2017-06-03 10:40 ` [PATCH] strbuf: let strbuf_addftime handle %z and %Z itself René Scharfe
2017-06-03 13:13 ` Ulrich Mueller
2017-06-03 16:20 ` René Scharfe
2017-06-07 8:17 ` Jeff King
2017-06-07 9:13 ` [PATCH] date: use localtime() for "-local" time formats Jeff King
2017-06-11 17:36 ` [PATCH] strbuf: let strbuf_addftime handle %z and %Z itself René Scharfe
2017-06-12 15:12 ` Junio C Hamano
2017-06-12 16:16 ` Ævar Arnfjörð Bjarmason
2017-06-12 16:56 ` Ulrich Mueller [this message]
2017-06-12 17:53 ` Ævar Arnfjörð Bjarmason
2017-06-12 18:15 ` Junio C Hamano
2017-06-12 18:20 ` Jeff King
2017-06-12 19:02 ` Ævar Arnfjörð Bjarmason
2017-06-12 21:10 ` Jeff King
2017-06-13 6:23 ` Linus Torvalds
2017-06-12 22:31 ` René Scharfe
2017-06-13 10:16 ` Ævar Arnfjörð Bjarmason
2017-06-13 10:31 ` Ulrich Mueller
2017-06-12 16:58 ` René Scharfe
2017-06-12 17:36 ` Jeff King
2017-06-15 8:46 ` [PATCH v2] " René Scharfe
2017-06-15 11:27 ` Ulrich Mueller
2017-06-15 12:28 ` René Scharfe
2017-06-15 12:29 ` [PATCH v3] " René Scharfe
2017-06-15 13:49 ` Jeff King
2017-06-15 13:51 ` [PATCH 1/2] t0006: check --date=format zone offsets Jeff King
2017-06-15 13:52 ` [PATCH 2/2] date: use localtime() for "-local" time formats Jeff King
2017-06-15 16:12 ` René Scharfe
2017-06-15 21:40 ` Junio C Hamano
2017-06-16 12:18 ` Jeff King
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