ludo@gnu.org (Ludovic Courtès) writes:

> Now the question is, will it always be possible to run ‘guix pull’ from
> an arbitrary-old Guix?  Maybe it will still be impossible sometimes if
> the old Guix is really too old.

Isn't this already possible?

If moving from Guix version 0.15 to 0.18, one can upgrade step by step
in each version separately:

guix pull --branch=0.16.0
guix pull --branch=0.17.0
guix pull # already pre-latest

This is even possible with Guix versions before the '--branch' option,
using '--url' instead.

As long as Guix can upgrade itself from each version, this should work
for any version upgrade.