bug#20206: 25.0.50; [PATCH] keep diff-mode's window visible when we visit sources from diff-mode

[Eli Zaretskii]

> Date: Mon, 13 Apr 2015 14:14:14 +0200
> From: martin rudalics <rudalics@gmx.at>
> Cc: help-gnu-emacs@gnu.org
> 
>  > The change in behavior is when there are already two buffers being shown, 
> with different files. So, with two files, a and b:
>  >
>  >
>  > $ emacs -Q a b
>  >
>  > I get just "b" displayed.
>  >
>  > ^X^B^Xo, cursor down, Enter.
>  >
>  > I get the "b" file in the top window, "a" file in the bottom window, with 
> the cursor in the "a" file's window.
>  >
>  >
>  > ^X^B
>  >
>  > The buffer window now replaces the "a" file, where the cursor was, and the 
> cursor now winds up in the buffer list window. That's the different behavior 
> than what I'm used to.
>  >
>  >
>  > Now, if instead of doing ^X^B at this point, I press ^Xo, moving the 
> cursor back to the "b" file's window, then ^X^B still opens the list buffer 
> in the "a" file's window (also).
>  >
>  >
>  > So, maybe the change in behavior is that list-buffers' window is "sticky", 
> and it tries to open the buffer window in the same window it was previously 
> shown in, apparently. If that window is showing another file buffer, even if 
> the cursor is still in that file buffer the buffer list window still gets 
> opened there, replacing the buffer the cursor was in.
>  >
>  >
>  > So, depending on window history, ^X^B ends up either opening the buffer 
> list window in some other window, than the one the cursor is currently in, or 
> the same window where the cursor is. I'm pretty sure that in earlier versions 
> of emacs, ^X^B never opened the list buffer in the same window the cursor 
> was, at the time the list-buffers command was executed.
>  >
>  >
>  > And that's where my muscle memory is failing me now. I'm used to having 
> multiple windows open; and with the cursor in one of them, ^X^B opening the 
> buffer in some other window, and then typing ^Xo to jump into the buffer list 
> window. Now, depending on where the buffer-list window was previously shown, 
> it will now open in the same window with the cursor, and I realize belatedly, 
> after I already jumped somewhere else with ^Xo.
> 
> Your explanation is correct.  The behavior is intended as a feature but
> inherently breaks the behavior of `pop-to-buffer', especially when used
> interactively.  I intend to fix this soonish for Emacs 25 and also post
> a simple workaround you can use for Emacs 24.4.

I think the following piece of magic will do what Sam wanted:

  (setq display-buffer-alist
        '(("\\*Buffer List\\*" .
           (display-buffer-pop-up-window '((inhibit-same-window . t))))))

If this is desired for all buffers, the regexp should be changed to
something that matches any buffer name.