bug#24346: [PATCH] Generate grub.cfg with correct paths when store is not in root partition

[ludo@gnu.org (Ludovic Courtès)]

Hi Carlos!

csanchezdll@gmail.com (Carlos Sánchez de La Lama) skribis:

> Rebasing to current master (76f31f0b), as new file-append made merge
> non-trivial.
>
> * guix/scripts/system.scm (previous-grub-entries): resolve initrd
>   symlink for old entries (on the host).
> * gnu/system.scm (operating-system-grub.cfg): resolve initrd symlink for
>   current system (on the container).
> * gnu/system/grub.scm: strip mount-point from GRUB filenames.

I ended up pushing a slightly modified version of this patch as
0f65f54ebd76324653fd5506a7dab42ee44d9255.

Essentially, I was dissatisfied with those ‘readlink’ calls, which do
I/O and could always fail, so I changed them to use the procedures we
have that return the store file name of the initrd.

> +(define (strip-mount-point fs file)

I added a docstring here.

> +  (let ((mount-point (file-system-mount-point fs)))
> +    (if (string=? mount-point "/")
> +	file
> +	#~(if (string-prefix? #$mount-point #$file)
> +	      (substring #$file (string-length #$mount-point))
> +	      #$file))))

I introduced a ‘file’ variable in the staged code, to avoid having that
(string-append …) expression several times in the output.

I think that’s it!

I verified the grub.cfg that ‘guix system reconfigure’ generates and it
seems to work fine.  If you can confirm that it still works for you,
please say so to 24346-done@debbugs.gnu.org.  :-)

Thanks a lot for addressing this bug!

Ludo’.