[tex-k] Reproducible builds using pdftex

[pado at passoire.fr]

Le 02/05/2016 19:53, Karl Berry a écrit :
> I understood from previous discussions that you don't want to change the
> build processes to require tinkering with the TeX sources or adding
> command line options.

That is the point, you're right. A lot of software packages are
concerned, and fixing all of them is a real hard work.

> So I can imagine supporting a second envvar,
> something like SOURCE_DATE_EPOCH_TEX_PRIMITIVES, which would need to be
> set to enable these changes as well.

This could be OK.
However, I'm wondering:
- What is the advantage of dealing with the two envvars
SOURCE_DATE_EPOCH and SOURCE_DATE_EPOCH_TEX_PRIMITIVES instead of one?
- And what will be the difference? In our build process, I think we will
set both envvars to the same value for all packages to be built.

> By the way, for your real builds, are you setting SOURCE_DATE_EPOCH to
> the build date, or last mtime for the doc sources, or something?  Not
> actually zero, right?   --thanks, k.

Actually, the last debian/changelog date, which is the last date the
source files were modified. This won't be zero.
That is: when building the software documentation, with the help of the
envvar, pdftex will behave as if this was called right after the last
source change.

Regards,
Alexis Bienvenüe.