It seems that at least two additional problems remain to achieve reproducible examples.tar.gz construction:
* File order (e.g. by name) in the tarfile needs to be consistent. * File permissions - that currently may differ based on build-time umask, I'm not certain of the cause yet - need to be consistent. A fix for the former is documented[1] on the Reproducible Builds website, and there would seem to be at least two options for the latter (either ensure that the files that are read for inclusion into the tarball have consistent permissions before it is created, or update the tar command-line to configure static permissions). I plan to file a separate bug to report this (hopefully within the next 24h or so), ideally with a patch and tested properly using reprotest. [1] - https://reproducible-builds.org/docs/archives/
