To summarise, when-let/if-let have been deprecated in Emacs 31 so it is
best to stick to the star'ed variants.  The rewriting of
`eldoc-diffstat--format-output-buffer' might be controversial, but I
feel that using a regular expression to destruct the buffer feels more
robust.

It would also be nice if you could add a .elpaignore file to exclude the
screenshot from being bundled with the tarball.

> It provides a way to display VCS diffstat information via eldoc.  I.e.,
> if point rests on a commit in a magit, vc-annotate, or log-view buffer,
> the Git or Mercurial diffstat summary will be shown in the echo area.
> For example (though it uses ansi-colors and fontification, so you might
> prefer to look at the screenshot in the repo):
>
>   Johann Klähn <xyz@localhost>, Thu, 3 Oct 2024 15:45:10 +0200: Minor refactoring
>    1 file changed, 93 insertions(+), 62 deletions(-)
>    eldoc-diffstat.el | 155 ++++++++++++++++++++++++++++++++----------------------
>
> It's adapted from Tassilo Horn's 2022 blog post “Using Eldoc with Magit
> (asynchronously!)”: https://www.tsdh.org/posts/2022-07-20-using-eldoc-with-magit-async.html
>
> Thanks
> Johann