Madduck wondered why a package using revision control needed pristine tarballs at all.

Firstly, the example he gave of tagging an upstream release and creating a tarball of it to build the package against is exactly what pristine-tar does. Except it preserves permissions and timestamps and other tar cruft.

Sometimes timestamp or permissions issues do cause issues with package builds, so being able to build against the original files from the pristine tarball is potentially useful to catch and fix such problems.

As to other uses of pristine tarballs...

It's hard to list the advantages to using pristine tarballs, since Debian (rpm too) has had them forever, and lots of people may depend on them in ways that we don't anticipate. For example, I've seen FreeBSD point at ftp.debian.org to get tarballs for their packages, since they don't archive tarballs on their own, and sometimes the tarball isn't available upstream (or ftp,debian.org is the upstream). That's a wacky example, but I've seen it more often than I've seen pristine tarballs used for the often-cited md5sum comparison case.

Rather than try to enumerate all the possible reasons for pristine tarballs, and then try to whittle the list down to reasons that actually make sense, and cost-benefit analise those, it seemed better to just try to write a solution to the problem. (Or at least, to most of it -- a hopefully small subset of the set of reasons for pristine tarballs are not satisfied by pristine-tar.)

I've also been theoretically interested in this problem of generating pristine tarballs from version controlled source ever since Scott Remnant mentioned at a meeting (140 mb video of meeting here) that he had a tool to do it -- and AFAIK never shared the tool! So the challange factor was another reason to write it.

However, pristine-tar has already saved me hundreds of megabytes of disk space, sped up my release process (avoiding Debian bug #225483) and simplified the way I work, so it's already a net win for me, even if it turns out we don't need pristine tarballs for anything at all!