bug#12855: 24.2; The Messages buffer stops following the appended lines.

[Yves Baumes]

Let's split the frame in two windows only, one for the *scratch* and the
other for *Messages*. From here you have a few lines only in the
*Messages* buffer. And untill now, every new lines introduced because of
a command output is followed. Moreover, I can see the "ghost" cursor at
the end of the buffer and it follows every *Messages* buffer updates.

Then, from the *scratch* buffer, I call the describe-variable key
sequence ( C-h v xxx ). The current buffer being *scratch*, the
*Messages* buffer will be replaced with the *help* buffer.

After finishing to read the description I want to quit it, because I
want the *Messages* buffer to come back. For that, I do: C-x o, thus
switching to the focus to the *Help* buffer, and I just type in 'q' to
quit it and instantly focus back to the *scratch* buffer.

But: When I look into the *Messages* buffer, the "ghost" cursor is no
longer at the same place. It has moved in the middle of the buffer. From
there, the window position relative to the buffer remains the same.
Which is not good because I want to see the *Messages* updates when they
come in.

Regards
Yves.