partman-auto early_command preseeding requiring backslash? (was: Bug#988140: Probably broken code example in installation-guide Appendix B.5 (Running custom commands))

[Samuel Thibault <sthibault@debian.org>]

Hello,

Boyuan Yang, le jeu. 06 mai 2021 11:10:41 -0400, a ecrit:
> I received a user report that
> https://www.debian.org/releases/bullseye/amd64/apbs05.en.html#preseed-hooks
> provides an incorrect code example:
> 
> # This command is run immediately before the partitioner starts. It may be
> # useful to apply dynamic partitioner preseeding that depends on the state
> # of the disks (which may not be visible when preseed/early_command runs).
> #d-i partman/early_command \
> #       string debconf-set partman-auto/disk "$(list-devices disk | head -n1)"
> 
> The reporter claims that the $ sign should be escaped, like:
> 
> #d-i partman/early_command \
> #    string debconf-set partman-auto/disk "\$(list-devices disk | head -n1)"

I guess the reporter actually tested that the backslash is needed. But
do we really want to have to put a backslash here, and thus it's the
documentation that needs to be fixed, or is it partman-auto which is
bogus and should rather be fixed?

Samuel