Re: fix for bug#29935 copyright-update inserts year at random places

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> Apparently completion (or maybe read-from-minibuffer) does re-iconify a
>> popped up frame (that happened once in my experiments). I looked thru
>> the C code for read-from-minibuffer, and it has comments that talk about
>> preserving the frame state, but I did not see where it minimizes the
>> frame on return. So I don't know how to do that from elisp in
>> copyright-update-year.
>
> There is one function `frame-auto-hide-function' and two frame
> parameters `auto-hide-function' and `minibuffer-exit' which can be
> useful in this context.

But this is a fairly normal/common need: display a buffer temporarily.
So we should have a "canned" answer.
I'm thinking of something like

    (let ((x (temporary-display-buffer BUF)))

    +

    (temporary-undisplay-buffer x)

where hopefully this would handle the case where
temporary-display-buffer needs to use a separate frame, as well as the
case where BUF is already displayed somewhere.


        Stefan