Hi Eli,

This is regarding a small prospective change to ERC on Emacs 29 that's
been discussed here and there over the past few months [1]. Basically,
ERC has long defaulted to displaying new buffers in the currently
selected window, with the symbol `buffer' representing this display
style in various user options. Because new buffers are often created as
a result of server-initiated messages or feature-driven automated
mechanisms, like "autojoin", they can suddenly appear unceremoniously
and steal keyboard input. For this reason, `buffer' was deemed a
nuisance (if not a hazard), and the default was changed to a no-op in
ERC 5.5 [2].

However, since then, a faint but steady murmur of discontent has been
thrumming among mostly new and casual users, who've described ERC as
being "broken" in this regard because it provides little to no obvious
feedback following certain fundamental user actions, like connecting to
a server or joining a channel. IOW, users can't tell whether ERC is
responding to a command they've just issued, despite subtle cues, like
activity in the echo area and the mode line.

The solution to all this isn't straightforward, and we're making headway
on it for ERC 5.6. In the meantime, I'm wondering if we might consider
appeasing these disgruntled users somehow. Normally, I'd prefer just
reverting back to `buffer', but because much has been made about its
potential for causing mayhem via unintended sharing, I'm thinking we
might change the default in Emacs 29 to `window-noselect'. This value
tells ERC to show new buffers in a sibling window of the same vertical
combination. Such a change would be accompanied by a bump in the patch
component of our already 29-specific ERC version, bringing us from
5.5.0.29.1 to 5.5.1.29.1. I believe the attached patch does what I've
described.

Thanks,
J.P.

[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=60428#31
    https://debbugs.gnu.org/cgi/bugreport.cgi?bug=62833#17
    https://debbugs.gnu.org/cgi/bugreport.cgi?bug=62833#23

[2] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=51753#71