Brian Inglis wrote:
If someone could contribute such a regression test script and baseline output
That's been done in the past (contributed privately to me), but my impression is that it wasn't ready for widespread publication and use, and was meant more for internal private use. I do internal regression testing on an ad-hoc basis, and I've recently been talking with a Large Development Organization to try to do this sort of thing more regularly with the tz data, but we don't have anything publishable yet.
normal revision control practice is to create a (tagged) branch for each potential change
That may be normal in some organizations, but it is neither common everywhere nor needed here. That approach inevitably leads to configure-time complexity on downstream installers, developers, and users, complexity that in our case would cause more harm than the practice would cure. Because the tz database is so small and stable that it's feasible for one very-part-time volunteer to merge everything into a single branch that's almost always near production quality, tagged branches wouldn't bring that much to the table. It'd of course be OK if contributors wanted to take the time to make a tagged branch for each potential change, but as far as I know no tz contributor does that now and I'd rather not impose that kind of version-control bureaucracy on future contributors (including myself :-).