On Mon, Jun 12, 2017 at 6:56 PM, Ulrich Mueller <u...@gentoo.org> wrote: >>>>>> On Mon, 12 Jun 2017, Ęvar Arnfjörš Bjarmason wrote: > >> On Mon, Jun 12, 2017 at 5:12 PM, Junio C Hamano <gits...@pobox.com> wrote: >>> René Scharfe <l....@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.)
Yes, I understand that it's a 1:many not a 1:1 mapping. What I'm saying is that %Z in the context of git-log means a human readable timezone name, and we can just make a best-effort at guessing that by picking 1/many out of the 1:many mapping. This obviously doesn't give us the user's timezone, but when you're browsing through git log you can get an approximate human-readable idea of what timezone someone was located in, and that's the whole point of %Z in the context of how it would be used via git-log, isn't it? >> 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. It's not invented information. %z being +0900 is the same thing as %Z being JST since +0900 == JST, just because some other things are also == +0900 that doesn't mean that JST is invalid or less useful than +0900 or "" for the purposes of human-readable output.
