bug#67310: [PATCH] Include the project--list as history when prompting for a project

[Juri Linkov]

>>>> This change broke the order of 'C-x p p M-n M-n ...',
>>> Could you remind me which behavior in 'M-n M-n' the aforementioned change
>>> relates to? Is this supposed to be like input history as well, or the
>>> contents of the completions table in a certain order?
>> It's inappropriate to overwrite the history with the recently visited 
>> projects.
>> Only user input should be added to history variables because it's actually
>> the history of user input.  Therefore, the remaining way to access a list
>> of recently visited projects is the future history with 'M-n M-n'.
>
> But... we do overwrite it now, manually constructing the value of input
> history from project--list every time.
>
> So it seems like both "past history" and "future history" show the same
> information now. If so, it might make sense to keep only one.

It's usually not good to overwrite past history.  So it's better
to keep only future history.

>>> I just tried find-file, and the future history is empty there, so I suppose
>>> this is something we added particularly for project-find-file.
>> Unlike with project--list, we don't keep a list of recently visited files.
>> Once we conducted an experiment to add all visited files to the input file 
>> history,
>> even when a file was visited without reading a file name in the minibuffer,
>> e.g. by typing RET in Dired.  But no one liked this behavior.
>
> I don't remember that experiment,

It was in https://debbugs.gnu.org/12915#121

#+begin_src emacs-lisp
(add-hook 'first-change-hook 'add-file-name-to-history)
(add-hook 'find-file-hook 'add-file-name-to-history)
(defun add-file-name-to-history ()
  (when (and buffer-file-name (not buffer-read-only))
    (add-to-history 'file-name-history buffer-file-name)))
#+end_src

but this clutters the file history too much.

> but the description sounds like recentf. Which must have its audience
> (and I use it through Ido's "virtual buffers").

'recentf-list' looks like the right thing to add to future history
of 'C-x C-f', but not to its past history.  This prototype works nicely:

#+begin_src emacs-lisp
(define-advice find-file (:around (ofun &rest args) recentf-list)
  (interactive (lambda (spec)
                 (minibuffer-with-setup-hook
                     (lambda ()
                       (when (featurep 'recentf)
                         (setq-local minibuffer-default-add-function
                                     (lambda () recentf-list))))
                   (advice-eval-interactive-spec spec))))
  (apply ofun args))
#+end_src

so this could be enabled by default when recentf.el is loaded.