bug#53885: 28.0.51 [PATCH] Autoload package-installed-p

[Corwin Brust]

On Wed, Feb 9, 2022 at 2:16 PM Lars Ingebrigtsen <larsi@gnus.org> wrote:
>
> It should be safe for the release branch, so installing it is fine by
> me, but I didn't really understand the use case.

Sorry I failed in making the case for users clear.

The primary use-case here is "repeatable configuration", especially
bootstrapping `use-package'.

By "repeatable configuration" we mean, we get the same setup each time
we start Emacs, even when launching for the first time on a new host.

The use package feature provides an "ensure" capability that is well
suited to this job.

  (use-package 'foo :ensure t)

This appears widely used, especially to create literate Emacs configurations.

For this to work, however, "bootstrapping" (installing use-package via
Emacs core features) is needed.  The reproducer I gave shows one way
of bootstrapping use-package. Considering the similarity of my
reproducer to the recipe in #31397, I think it is a fairly common
approach and has been for some years.