Being less flippant about this - the xz backdoor relied on a line that was present in the tarball release, but not in the git repo. Do we have any infrastructure for validating this kind of thing? (It's expected that the tarball would contain things that aren't in git - for example, the configure script doesn't exist in git, but is expected to be in the release. The problem is that extra code was injected into the configure script after it was generated)