Hey #Guix!

Now `guix pull` and `guix time-machine` supports Git symref. And?

It allows to easily have unmerged Pull-Request.

Consider the fictive PR 567 improving package foo.
And such CI processed this PR with the evaluation 1234.

Then

guix time-machine \
-C https://guix.bordeaux.inria.fr/eval/1234/channels.scm \
-- shell foo bar

where channels.scm file points to refs/pull/567/head.

Done! 🤩