[Reproducible-builds] Bug#787444: help2man: support externally-supplied --date for reproducibility

[Daniel Kahn Gillmor]

Hi Brendan--

Thanks for the quick followup! (cc'ing the r-b list)

On Wed 2015-06-03 08:24:51 -0400, Brendan O'Dea wrote:
> On 2 June 2015 at 04:49, Daniel Kahn Gillmor <dkg at fifthhorseman.net> wrote:
>> Please consider the attached patch as a step on the way toward allowing
>> packages that use help2man to build reproducibly.  For more info, see:
>
> I appreciate that you've provided a relatively generic solution to
> your problem: adding an option to set the date, but it occurs to me
> that most users don't actually care.  Additionally, this will require
> changing the builds for anything which uses help2man to add a --date
> option.

You're right, and that might make the fix take longer to take effect.
But it's not a terrible cost, and we have other packages in that same
situation.
 
> My inclination is instead to do something fairly specific to your
> project: If the environment variable DEB_BUILD_CHANGELOG (or something
> similar) is set, then the file to which it refers will be used to find
> the latest revision date, and that date will be used on the manual
> pages.  Presumably the build system could set this prior to
> build/test?

i think this could work, but it might not apply particularly well to
anyone outside of debian who uses help2man.  I note that help2man is a
native package -- do you know if it's used outside of debian at all?

Making the help2man run dpkg-parsechangelog also seems a little hairier
than it ought to be, and introduces a dependency on dpkg-dev which seems
a little weird.

If the build system is going to set environment variables, maybe it
could set an environment variable with a parseable date string
(ISO-8601?) and help2man could look at that environment variable and
extract a string from it?  (ideally this extraction step would be
TZ-independent, too)

What do you think?

     --dkg