bug#55360: [Installer] ‘guix system init’ displays dots instead of progress bars

[Ludovic Courtès]

Hi!

I’ve used an installer built from this commit:

--8<---------------cut here---------------start------------->8---
Generation 214  May 02 2022 21:44:14    (current)
  guix 6b588da
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 6b588da368c77cde82ea2f22ca315116228777ad
--8<---------------cut here---------------end--------------->8---

During installation, ‘guix system init’ displays dots instead of
progress bars for downloads and such.

This suggests that ‘display-download-progress’ gets #:tty? #f.  This may
be a side effect of running it in a pipe in
‘run-external-command-with-handler’.

Thoughts?

Ludo’.