Hi Simon, > What about this patch? That's a good start! But I didn't quite understand what "as defined by the previous +@dfn{channels} file" means, so I did some more research and some more rewriting, and came up with the attached patch. That one is clear for me, but maybe not for others... In the course of this research, I noticed that channel files are used in Guix in two varieties for rather different purposes, but this doesn't seem to be explained anywhere. "guix describe -f channels" produces channel files with a pinned commit for each repository. That's what we usually give to time-machine. That feature of channel files seems even undocumented. The chapter on channels discusses the channel files we typically use with "guix pull", and which refer to a branch and thus its last commit, rather than to a pinned commit. Cheers, Konrad.