Hi Ludo,

> >  (define* (repack #:key inputs #:allow-other-keys)
> > -  (invoke "tar" "-czf" "../package.tgz" ".")
> > +  (invoke "tar"
> > +          ;; Add options suggested by https://reproducible-builds.org/docs/archives/
*
> > +          "--sort=name"
> > +          (string-append "--mtime=" (getenv "SOURCE_DATE_EPOCH"))
> 
> I think it should be "--mtime=@".
you’re right, fixed.

> I didn’t know about this ‘--pax-option’ trick; since it’s only useful
> when POSIXLY_CORRECT is set, perhaps we can remove it?
True, removed.

> (guix docker) does this:
> and (guix packages) does something similar.
Hm, maybe it would make sense to export a set of options, so
build systems/packages can share them? Or create a package that wraps
tar with the proper options?

> So ‘--sort=name’ seems to be missing.
It’s present, see above ↑*

Updated patch attached. I’ll push it if there are no further comments.

Cheers,
Lars