doc: Proposed note about symlinks in section "invoking guix pull"

[swedebugia <swedebugia@riseup.net>]

[-- Attachment #1: Type: text/plain, Size: 1472 bytes --]

Hi

The manual reads:

"This |~/.config/guix/current| profile works like any other profile 
created by |guix package| (see Invoking guix package 
<https://www.gnu.org/software/guix/manual/en/html_node/Invoking-guix-package.html#Invoking-guix-package>). 
That is, you can list generations, roll back to the previous 
generation—i.e., the previous Guix—and so on:

$ guix package -p ~/.config/guix/current --roll-back
switched from generation 3 to 2
$ guix package -p ~/.config/guix/current --delete-generations=1
deleting /home/charlie/.config/guix/current-1-link"

Users without a working guix is not helped by this.
Ie they get errors when trying to run guix package -p ...:
"Missing guile-gcrypt bla bla"

I suggest a note below this saying:
"Note: if your have wound up with a faulty guix after a "guix pull" you 
can manually run an older version by looking at the symlinks in your 
/user/home/.config/guix/ directory.
E.g. if it lists:
$ ls -l /root/.config/guix/
total 0
lrwxrwxrwx 1 root root 33 Nov  4 01:24 current -> 
/root/.config/guix/current-1-link
...
Then your faulty guix is in current-1-link, and your former probably 
well working guix is in an older symlink, e.g. current-2-link.
To run the guix-version before the last pull in the example above, run:
/root/.config/guix/current-2-link/bin/guix

Now go ahead and use that older guix to roll back as described above."

What do you think?
-- 
Cheers Swedebugia

[-- Attachment #2: Type: text/html, Size: 2113 bytes --]