* test/lisp/erc/erc-scenarios-log.el (erc-scenarios-log--truncate):
Mark :unstable for now.
* test/lisp/erc/resources/base/renick/queries/solo.eld: Timeouts.
* test/lisp/erc/resources/base/reuse-buffers/channel/barnet.eld: Timeouts.
* test/lisp/erc/resources/base/reuse-buffers/channel/foonet.eld: Timeouts.
* test/lisp/erc/resources/erc-scenarios-common.el: Timeouts.

* test/lisp/erc/erc-tests.el
(erc-tests--assert-printed-in-subprocess): Don't insist that arguments
to the Emacs "-load" invocation option be actual disk files.
* test/lisp/erc/resources/erc-d/erc-d-t.el
(erc-d-t--wait-message-prefix, erc-d-t-wait-for, erc-d-t-ensure-for):
Add and use new variable to make `ert-info' message prefix adjustable.
The immediate use for this is to make it easier to distinguish between
consecutive assertions in which the first waits for a condition and
the second ensures it holds for some duration.
* test/lisp/erc/resources/erc-d/erc-d-u.el
(erc-d-u--read-exchange-default): Skip killed buffers.
* test/lisp/erc/resources/erc-d/erc-d.el: Typo.
* test/lisp/erc/resources/base/assoc/bouncer-history/barnet.eld: Timeouts.
* test/lisp/erc/resources/base/assoc/bouncer-history/foonet.eld: Timeouts.
* test/lisp/erc/resources/base/assoc/bumped/again.eld: Timeouts.
* test/lisp/erc/resources/base/assoc/bumped/foisted.eld: Timeouts.
* test/lisp/erc/resources/base/assoc/bumped/refoisted.eld: Timeouts.
* test/lisp/erc/resources/base/flood/soju.eld: Timeouts.
* test/lisp/erc/resources/base/netid/bouncer/barnet.eld: Timeouts.
* test/lisp/erc/resources/base/netid/bouncer/foonet.eld: Timeouts.
* test/lisp/erc/resources/base/reconnect/aborted-dupe.eld: Timeouts.
* test/lisp/erc/resources/base/reconnect/aborted.eld: Timeouts.
* test/lisp/erc/resources/base/renick/self/qual-chester.eld: Timeouts.
* test/lisp/erc/resources/base/renick/self/qual-tester.eld: Timeouts.
* test/lisp/erc/resources/erc-d/resources/dynamic-barnet.eld: Timeouts.
* test/lisp/erc/resources/erc-d/resources/dynamic-foonet.eld: Timeouts.
* test/lisp/erc/resources/erc-d/resources/linger.eld: Timeouts.
* test/lisp/erc/resources/join/legacy/foonet.eld: Timeouts.

There have been three failures (all on native-comp-speed2-master) over
the last three weeks pointing to these tests, which haven't changed in
the year-plus they've existed in tree.  No test appears in multiple
failures, and all continue to pass daily on commercial GitLab (GCP)
runners using the same EMBA container image.  They also pass locally
with "make check" and "make -j -C test SELECTOR=t check-lisp-erc".  If
these tweaks don't fix the problem, they can be branded :unstable.

* test/lisp/erc/erc-scenarios-base-renick.el: Extend timeouts.
* test/lisp/erc/resources/base/netid/bouncer/barnet.eld: Extend
timeouts.
* test/lisp/erc/resources/base/netid/bouncer/foonet.eld: Extend
timeouts.
* test/lisp/erc/resources/base/reconnect/options.eld: Extend timeouts.
* test/lisp/erc/resources/base/renick/queries/bouncer-barnet.eld:
Extend timeouts.
* test/lisp/erc/resources/base/renick/queries/bouncer-foonet.eld:
Extend timeouts.
* test/lisp/erc/resources/erc-scenarios-common.el: Extend timeout.
* test/lisp/erc/resources/services/auth-source/libera.eld: Extend
timeouts.

This reverts commit 8c0c98268440b27a77faf30738dfd72c909bb33f.  The
functionality it introduced is likely being migrated to a
"regain"-specific local module to live in the library erc-services.el
alongside the existing `services' module.  Its scope will be expanded
to address common "regain" cases requiring NickServ.  This commit is
being reverted to prevent any confusion that might arise from users
encountering the old interface while the new one is being hashed out
on the tracker.

* lisp/erc/erc-backend.el (erc-server-reconnect-timeout): Mention
`erc-nickname-in-use-functions' in doc string.
* lisp/erc/erc.el (erc-nickname-in-use-functions,
erc-regain-nick-on-connect): Add abnormal hook and possible value to
handle stale connections preventing a desired nick from being reissued
by the server.  Follows directly from bug#62044.
(erc-nickname-in-use): Call `erc-nickname-in-use-functions'.
* test/lisp/erc/erc-scenarios-base-renick.el
(erc-scenarios-base-renick-auto-regain): New test.
* test/lisp/erc/resources/base/renick/regain/normal-again.eld: New file.
* test/lisp/erc/resources/base/renick/regain/normal.eld: New file.

* test/lisp/erc/erc-scenarios-base-association-nick.el: New file.
* test/lisp/erc/erc-scenarios-base-association-samenet.el: New file.
* test/lisp/erc/erc-scenarios-base-association.el: New file.
* test/lisp/erc/erc-scenarios-base-compat-rename-bouncer.el: New file.
* test/lisp/erc/erc-scenarios-base-misc-regressions.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-id.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-recon-base.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-recon-both.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-recon-id.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-samenet.el: New file.
* test/lisp/erc/erc-scenarios-base-reconnect.el: New file.
* test/lisp/erc/erc-scenarios-base-renick.el: New file.
* test/lisp/erc/erc-scenarios-base-reuse-buffers.el: New file.
* test/lisp/erc/erc-scenarios-base-unstable.el: New file.
* test/lisp/erc/erc-scenarios-base-upstream-recon-soju.el: New file.
* test/lisp/erc/erc-scenarios-base-upstream-recon-znc.el: New file.
* test/lisp/erc/erc-scenarios-misc.el: New file.
* test/lisp/erc/erc-scenarios-services-misc.el: New file.
* test/lisp/erc/resources/base/assoc/bouncer-history/barnet.eld: New file.
* test/lisp/erc/resources/base/assoc/bouncer-history/foonet.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/again.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/foisted.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/refoisted.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/renicked.eld: New file.
* test/lisp/erc/resources/base/assoc/multi-net/barnet.eld: New file.
* test/lisp/erc/resources/base/assoc/multi-net/foonet.eld: New file.
* test/lisp/erc/resources/base/assoc/reconplay/again.eld: New file.
* test/lisp/erc/resources/base/assoc/reconplay/foonet.eld: New file.
* test/lisp/erc/resources/base/assoc/samenet/chester.eld: New file.
* test/lisp/erc/resources/base/assoc/samenet/tester.eld: New file.
* test/lisp/erc/resources/base/assoc/samenet/tester2.eld: New file.
* test/lisp/erc/resources/base/channel-buffer-revival/foonet.eld: New file.
* test/lisp/erc/resources/base/flood/soju.eld: New file.
* test/lisp/erc/resources/base/gapless-connect/barnet.eld: New file.
* test/lisp/erc/resources/base/gapless-connect/foonet.eld: New file.
* test/lisp/erc/resources/base/gapless-connect/pass-stub.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/barnet-again.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/barnet-drop.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/barnet.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/foonet-again.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/foonet-drop.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/foonet.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/stub-again.eld: New file.
* test/lisp/erc/resources/base/netid/samenet/chester.eld: New file.
* test/lisp/erc/resources/base/netid/samenet/tester.eld: New file.
* test/lisp/erc/resources/base/reconnect/aborted-dupe.eld: New file.
* test/lisp/erc/resources/base/reconnect/aborted.eld: New file.
* test/lisp/erc/resources/base/reconnect/options-again.eld: New file.
* test/lisp/erc/resources/base/reconnect/options.eld: New file.
* test/lisp/erc/resources/base/reconnect/timer-last.eld: New file.
* test/lisp/erc/resources/base/reconnect/timer.eld: New file.
* test/lisp/erc/resources/base/renick/queries/bouncer-barnet.eld: New file.
* test/lisp/erc/resources/base/renick/queries/bouncer-foonet.eld: New file.
* test/lisp/erc/resources/base/renick/queries/solo.eld: New file.
* test/lisp/erc/resources/base/renick/self/auto.eld: New file.
* test/lisp/erc/resources/base/renick/self/manual.eld: New file.
* test/lisp/erc/resources/base/renick/self/qual-chester.eld: New file.
* test/lisp/erc/resources/base/renick/self/qual-tester.eld: New file.
* test/lisp/erc/resources/base/reuse-buffers/server/barnet.eld: New file.
* test/lisp/erc/resources/base/reuse-buffers/server/foonet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/soju-barnet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/soju-foonet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/znc-barnet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/znc-foonet.eld: New file.
* test/lisp/erc/resources/erc-scenarios-common.el: New file.
* test/lisp/erc/resources/networks/announced-missing/foonet.eld: New file.
* test/lisp/erc/resources/services/password/libera.eld: New file.

Add test cases for locking down fundamental client behavior, much of
it involving the relationship between buffers and connections.  Also
add accompanying resources subdir containing canned dialog scripts and
common code needed by various tests.  For test cases demoing the
problematic behavior originally described in the initial report, see
update #4 on the bug tracker thread for bug#48598.  Most reside in a
file named test/lisp/erc/erc-scenarios-48598.el introduced by the
patch "Add user-oriented test scenarios for ERC".