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

[Paul Eggert]

On 10/7/21 10:00 AM, Tom Lane via tz wrote:
> why isn't there an easy way to
> identify the release version of an installed tzdata tree?

$ head -n 1 /usr/share/zoneinfo/tzdata.zi
# version 2021b

I ran this shell command on my Fedora 34 system, which I updated a few 
days ago from the Fedora project by using the "dnf update", a standard 
way to keep up-to-date.

Unfortunately this tzdata.zi approach is not taken by every 
distribution. Also, it's reasonably common for distributions to say 
"2021b" (or whatever) even though the actual data contains minor 
modifications from vanilla 2021b. The modifications are typically so 
minor that almost nobody cares about the differences (though evidently 
somebody does :-).