Hi Paul, > > timestamp(Y) := max (vmtime(X1), vmtime(X2), ..., vmtime(Xn)). > > > > where vmtime(X) is defined as: > > > > - if X is under version control and not modified locally: > > $(git log -1 --format=%ct X), > > that is, the last time file X was modified under version control, > > - otherwise: mtime(X). > > This is roughly what I use for TZDB <https://iana.org/tz>, except with > the following additions: > > * timestamp(Y) is 1 + max (...), not merely max (...). This is for > portability to 'make' implementations that consider equal timestamps to > mean that the target needs rebuilding (POSIX suggests this behavior). > > * If X is built and is not under version control, then vmtime(X) is > timestamp(X) not mtime(X). This is needed for reproducibility when there > are long dependency chains.
Thanks for mentioning this. Re 1 + max: yes that makes sense, also for compensating a conversion to entire seconds, that loses fractional seconds. Re chains: yes, that makes sense as well. In my case, this applies to the po/POTFILES file, which is generated from po/POTFILES.in. The vmtime(po/POTFILES) needs to be ignored; the vmtime(po/POTFILES.in) is what matters instead. I see your rules in tz/Makefile, target 'set-timestamps.out'. This rule uses "git diff --quiet $$file". Shouldn't it use "git diff --quiet HEAD $$file" instead? I.e. treat a modification that was staged via "git add FILE" like a modification that was not staged? Bruno
