[tex-k] Reproducible builds using pdftex

[Karl Berry]

    SOURCE_DATE_EPOCH to also feed the values of the
    \year, \month and \day primitives.

Changing the meaning of TeX primitives is a vastly different scenario
from changing embedded PDF info.  I understand your need for it, but I
don't think it should be so easy to invalidate all existing TeX
documentation.

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.  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.

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.