bug#63627: Improve plstore.el and fix various issues of it

[Jens Schmidt via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

On 2023-09-08  07:40, Eli Zaretskii wrote:
>> Date: Thu, 7 Sep 2023 21:27:13 +0200
>> From: Jens Schmidt <jschmidt4gnu@vodafonemail.de>
>> Cc: 63627@debbugs.gnu.org

>> Not sure how you prefer to get such long-running projects presented -
>> as a series of minor (but self-contained!) patches over time or at
>> once as one big set of patches.
> 
> It is preferable to install separate patches only if each one of them
> has merit on its own.  E.g., imagine that some "force majeure" will
> prevent you from working on further changes, and ask yourself whether
> what you already have would make an improvement if installed.
> 
> Changes that only make sense together are better submitted and
> installed as a single patch.

Good to know, thanks.

> But if you personally prefer to submit a series of patches even when> they should be installed together, that's fine, it will just make them
> slightly harder to review, especially if they touch the same code.

Let's postpone the addition of the last outstanding patch, then.  I'll
add more tests to it and will come back to you later on this bug.

Independently of the tests, I'll do the Emacs 29 bugs next, also on this
bug.