bug#67993: Selecting buffer automatically

[Juri Linkov]

>> Could you suggest an alternative to 'old-selected-window'
>> to select the original window that was selected before
>> the current command?
>
> In 'display-buffer' first save the selected window as
> old-selected-window, display the buffer and in your code select
> old-selected-window instead of (old-selected-window).

Unfortunately, this is not so easy to do.  'old-selected-window'
should be reinitialized before the next command is executed.

So by definition 'old-selected-window' should contain
the window that was selected before the current command
was executed.  I have no idea how to do this without hooks.

> Better, rename "select-window" to "window-to-select" so grepping won't
> confuse it with a 'select-window' call and allow for an arbitrary window
> (or even buffer, but there could be two windows showing the same buffer)
> to use as the finally selected window in 'display-buffer'.  And maybe
> have 'pop-to-buffer' and friends pass (select-window . t) instead of
> calling 'select-window' themselves

'pop-to-buffer' can't be changed because (select-window . t)
should be handled only at the end of the current command.

> and think of what has to happen when the window made or used by
> 'display-buffer' is on another frame that should be (de-)selected.

So this also need to run 'select-frame' in post-command-hook.