Courtès: Connecting reproducible deployment to a long-term source code archive

On the Guix blog, Ludovic Courtis writes about connecting reproducible builds for the Guix package manager with the Software Heritage archive."It quickly became clear that reproducible builds had 'reproducible source code downloads', so to speak, as a prerequisite. The Software Heritage archive is the missing piece that would finally allow us to reproduce software environments years later in spite of the volatility of code hosting sites. Software Heritage's mission is to archive essentially 'all' the source code ever published, including version control history. Its archive already periodically ingests release tarballs from the GNU servers, repositories from GitHub, packages from PyPI, and much more.We quickly settled on a scheme where Guix would fall back to the Software Heritage archive whenever it fails to download source code from its original location. That way, package definitions don't need to be modified: they still refer to the original source code URL, but the downloading machinery transparently goes to Software Heritage when needed."