[tz] Version identification (was Re: Downstream use of 2021c)

[Tom Lane]

Paul Eggert via tz <tz at iana.org> writes:
> On 10/7/21 13:41, Arthur David Olson via tz wrote:
>> One odd possibility on standardizing access to version information: a 
>> zic'd line such as...
>>     Zone Version 0 - 2021c
>> ...would allow use of the command...
>>    TZ=Version date
>> ...to discover the version.-)

> Clever! I hadn't thought of that. This could supplant the "# version" 
> line in tzdata.zi, and I suppose a similar trick could be used for the 
> "# redo", "# ddeps", and "# dataform" lines - though this would limit us 
> to ASCII alphanumerics and '-' and '+' in version numbers, which could 
> be a bit restrictive.

Yeah, that's a cute idea.  I like it a bit better than my proposal,
because it offers the possibility of checking the TZ version through
APIs that don't necessarily offer direct access to the zoneinfo file
tree (mumble Postgres mumble).

			regards, tom lane