Revive option erc-query-on-unjoined-chan-privmsg

* etc/ERC-NEWS: Mention reinstated and renamed legacy option
`erc-query-on-unjoined-chan-privmsg' as well as a change in behavior
for `erc-auto-query', when nil.  Also fix erroneous ChangeLog
reference in 5.5 section.
* lisp/erc/erc-backend.el (erc-server-PRIVMSG): Consider flag
`erc-receive-query-display-defer' and revived option
`erc-query-unjoined-chan-privmsg' when deciding whether to create a
new query buffer.  And only "open" a buffer for an unknown target when
the latter option is non-nil.
* lisp/erc/erc.el (erc-cmd-QUERY): Make error more informative.
(erc-query): Revise deprecation message.
(erc-auto-query, erc-receive-query-display): Swap alias and aliased
and add option to `erc-buffers' group.  Mention the nonstandard
meaning of nil and update package-version to signify a behavioral
change, even though the default value remains untouched.
(erc-receive-query-display-defer): Add new variable, a compatibility
switch to access legacy behavior for `erc-auto-query'.
(erc-query-on-unjoined-chan-privmsg,
erc-ensure-target-buffer-on-privmsg): Revise doc string and add alias.
Change package-version to ERC 5.6 due to slightly refined meaning.
* test/lisp/erc/erc-scenarios-base-attach.el: New file.
* test/lisp/erc/resources/base/channel-buffer-revival/reattach.eld:
New file.  (Bug#62833)

1 files changed, 18 insertions, 5 deletions

diff --git a/etc/ERC-NEWS b/etc/ERC-NEWS
index 8f1b89f268b..6897993c628 100644
--- a/etc/ERC-NEWS
+++ b/etc/ERC-NEWS
@@ -45,9 +45,15 @@ security issue led to new ERC buffers being "buried" on creation.  On
 further reflection, this was judged to have been an overcorrection in
 the case of interactive invocations, hence the new option
 'erc-interactive-display', which is set to 'buffer' (i.e., "take me
-there") by default.  Accompanying this addition are "display"-suffixed
-aliases for related options 'erc-join-buffer' and 'erc-auto-query',
-which users have reported as being difficult to discover and remember.
+there") by default.
+
+Accompanying this addition are "display"-suffixed aliases for related
+options 'erc-join-buffer' and 'erc-auto-query', which users have
+reported as being difficult to discover and remember.  When the latter
+option (now known as 'erc-receive-query-display') is nil, ERC uses
+'erc-join-buffer' in its place, much like it does for
+'erc-interactive-display'.  The old nil behavior can still be gotten
+via the new compatibility flag 'erc-receive-query-display-defer'.
 
 ** Setting a module's mode variable via Customize earns a warning.
 Trying and failing to activate a module via its minor mode's Custom
@@ -108,6 +114,13 @@ other than the symbol 'erc-button-buttonize-nicks' appearing in the
 "FORM" field (third element) of this entry are considered deprecated
 and will incur a warning.
 
+** Option 'erc-query-on-unjoined-chan-privmsg' restored and renamed.
+This option was accidentally removed from the default client in ERC
+5.5 and was thus prevented from influencing PRIVMSG routing.  It's now
+been restored with a slightly revised role contingent on a few
+assumptions explained in its doc string.  For clarity, it has been
+renamed 'erc-ensure-target-buffer-on-privmsg'.
+
 ** Miscellaneous UX changes.
 Some minor quality-of-life niceties have finally made their way to
 ERC.  For example, the function 'erc-echo-timestamp' is now
@@ -332,8 +345,8 @@ In an effort to help further tame ERC's complexity, the variable
 'erc-default-recipients' is now expected to hold but a single target.
 As a consequence, functions like 'erc-add-default-channel' that
 imagine an alternate, aspirational model of buffer-target relations
-have been deprecated.  See Emacs change-log entries from around July
-of 2022 for specifics.
+have been deprecated.  Grep for their names in ChangeLog.4 for
+details.
 
 A number of less consequential deprecations also debut in this
 release.  For example, the function 'erc-auto-query' was deemed too