[Reproducible-builds] Reproducible patches for libisoburn and libisofs

[Chris Lamb]

Hi Thomas,

> - Verify that SOURCE_DATE_EPOCH works as promised and expected.
>   (Promised is to set the defaults of three xorriso settings.
>    Expected is that these defaults suffice for reliable reproducibility.)

My current schedule is to test this and report back in the next 4 or 5
days.

As a heads-up, I think I am likely to relax one change that might be
of interest. May I propose the following behaviour *iff* SOURCE_DATE_EPOCH
is set:

 - mtimes are taken from stat(2). [The FS creator is responsible for
   ensuring they are reproducible, possibly by some "clamping" call
   to `find -newermt | xargs touch …`.]

 - atime is copied from mtime [as FS creator "can't" set that].

 - ctime is copied from mtime [ditto].

This seems less like a giant hammer of setting them all to target->now.

 
> - Verify that bootable Debian ISOs made with xorriso-1.4.6 still work
>   as good or bad as those currently made with 1.3.6 (or maybe 1.4.4).

To clear up any ambiguity here, whilst I am making ISOs based on Debian,
they are not "Debian ISOs" in any sense of being connected with debian-cd
or being official in any sense. I am therefore not testing them from
the "Debian" point of view and ACKs are simply my own testcases.


Regards,

-- 
      ,''`.
     : :'  :     Chris Lamb
     `. `'`      lamby at debian.org / chris-lamb.co.uk
       `-