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Andrew Gierth authored
tzdb 2019a made "UCT" a link to the "UTC" zone rather than a separate zone with its own abbreviation. Unfortunately, our code for choosing a timezone in initdb has an arbitrary preference for names earlier in the alphabet, and so it would choose the spelling "UCT" over "UTC" when the system is running on a UTC zone. Commit 23bd3cec was backpatched in order to address this issue, but that code helps only when /etc/localtime exists as a symlink, and does nothing to help on systems where /etc/localtime is a copy of a zone file (as is the standard setup on FreeBSD and probably some other platforms too) or when /etc/localtime is simply absent (giving UTC as the default). Accordingly, add a preference for the spelling "UTC", such that if multiple zone names have equally good content matches, we prefer that name before applying the existing arbitrary rules. Also add a slightly lower preference for "Etc/UTC"; lower because that preserves the previous behaviour of choosing the shorter name, but letting us still choose "Etc/UTC" over "Etc/UCT" when both exist but "UTC" does not (not common, but I've seen it happen). Backpatch all the way, because the tzdb change that sparked this issue is in those branches too.
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