What's the idiomatic way to get new versions of guix packages? I've pinned the official guix channel to a specific git sha and every now and then I've been updating the sha by hand (after reviewing the release notes/skimming the commits) and running guix pull but that feels a bit unnatural. In addition to that, sometimes the packages there aren't the versions I want, for instance guix master still has emacs 27 and emacs-next-pgtk 28. In order to use emacs 29 I have to either find a channel that has it, roll my own or regress to a traditional package manager. How do you approach this?