As you know, ng0 was having trouble booting into GuixSD after 1ef8b72a7f87afe7cffe52393d99e1b14e4770e1. When I looked closely at the change, I realized we were not doing the right thing in all cases. Here is a patch to fix that.
I've confirmed via manual testing in a QEMU image that when using a device path for the file system containing the store, 'guix system reconfigure' does the right thing: it uses a file-based GRUB root search in the new GRUB menu entry. That's what it originally did, but 1ef8b72a7f87afe7cffe52393d99e1b14e4770e1 broke that behavior. I didn't catch this regression because our existing system tests did not catch it, and in all my manual tests, I was using file system labels, not device paths. -- Chris