bug#42653: Emacs now recentering very aggressively

[Eli Zaretskii]

> From: Dale Sedivec <dale@codefu.org>
> Date: Thu, 10 Sep 2020 16:18:55 -0500
> 
> 1. emacs -Q
> 
> 2. Display anything in the header line: (setq-default header-line-format 
> "foo")
> 
> 3. Open any file longer than a few screenfuls: M-x find-library RET subr RET
> 
> 4. Enable which-function-mode: M-x which-function-mode RET
> 
> (display-line-numbers-mode also triggers this problem, but I find 
> which-function-mode more interesting since it doesn't change the display of 
> the buffer at all, only the mode line.)
> 
> 5. M-> (end-of-buffer)
> 
> 6. Page up a few times with M-v (scroll-down-command)
> 
> Expected behavior: Point is sitting at the bottom line of the window no 
> matter how many times you page up
> 
> Observed behavior: The window is recentered, usually after ever page up, with 
> a slight delay

Thanks, there was a subtle thinko in commit a07ec21bf24b, should be
fixed now.