bug#33007: 27.0.50; Proposal for function to edit and return string

[Drew Adams]

> > Don't we already have something like that in Customize and/or in EWW,
> > where they allow the user to fill fields in a form?
> 
> The use cases I have in mind don't fit there.  If you for example want
> an interface to be able to attach multi line text notes to articles in
> Gnus, it makes no sense to use a Customize or EWW buffer for that.
> 
> `org-capture' is another (already implemented) example: It prompts you
> for a new note or task using a pop-up buffer.  This time, this buffer is
> in org mode.
> 
> Magit's buffer prompting for a commit message is yet another example.
> In all these cases, you don't yet have a buffer that you could use for
> input, unlike Customize or EWW, and the minibuffer is not good for the
> task.

Plus adding/editing a bookmark annotation, plus...

The need is a general one. And the appropriate modes for possible editing 
buffers are unlimited. And what-to-do-with-the-result-of-editing is also 
unlimited.

What's needed is a function that lets you specify such things: editing mode and 
a function (such as `read', for Lisp code) to apply to the buffer content after 
editing (i.e., as part of "sending" or returning it).

Also needed probably is some way to provide text to be inserted at the top of 
the buffer as instructions, suitably commented-out if needed.

(Alternatively, put such text in a separate pop-up buffer, like `M-x 
report-emacs-bug' does with (some of) its instructions/help.)