[bug#47163] [PATCH] doc: Add snippet for running 'guix refresh' on installed packages

[Ludovic Courtès]

Hi,

Xinglu Chen <public@yoctocell.xyz> skribis:

> * doc/guix.texi (Invoking guix refresh): Add snippet that runs 'guix refresh'
> on all the packages installed in the current profile.

[...]

> +You can also quickly update all the packages installed in the current
> +profile with the following snippet:
> +
> +@example
> +$ guix refresh -u $(guix package --list-installed | cut -f1)
> +@end example
> +
> +This is handy if you don't use manifests for installing packages into
> +your profile.

Note that if you type this literally, it fails along these lines:

--8<---------------cut here---------------start------------->8---
$ guix refresh -u grep

Starting download of /tmp/guix-file.yLXS45
>From https://ftpmirror.gnu.org/gnu/grep/grep-3.6.tar.xz...
following redirection to 
`https://gnu.mirror.constant.com/grep/grep-3.6.tar.xz'...
 …6.tar.xz  1.5MiB                    2.3MiB/s 00:01 [##################] 100.0%

Starting download of /tmp/guix-file.NgvvW4
>From https://ftpmirror.gnu.org/gnu/grep/grep-3.6.tar.xz.sig...
following redirection to 
`https://mirrors.ocf.berkeley.edu/gnu/grep/grep-3.6.tar.xz.sig'...
 …tar.xz.sig  833B                    1.8MiB/s 00:00 [##################] 100.0%
gpgv: Signature made Mon 09 Nov 2020 05:40:03 AM CET
gpgv:                using RSA key 155D3FC500C834486D1EEA677FD9FCCB000BEEEE
gpgv: Good signature from "Jim Meyering <jim@meyering.net>"
gpgv:                 aka "Jim Meyering <meyering@fb.com>"
gpgv:                 aka "Jim Meyering <meyering@gnu.org>"
gnu/packages/base.scm:99:12: grep: updating from version 3.4 to version 3.6...
guix refresh: error: mkstemp!: Read-only file system
--8<---------------cut here---------------end--------------->8---

So I think this example may be misleading.  We could instead suggest
./pre-inst-env, with a link to “Running Guix Before It Is Installed”,
and possibly mention the ‘--with-latest’ option as well.

WDYT?

Thanks,
Ludo’.