bug#70928: 30.0.50; ERC 5.6: Reuse query buffers for round-trip nick changes in ERC

[J.P.]

>From emacs -Q

  1. Start a new session, connecting as nick A
  2. Start another session, connecting as nick B
  3. As nick B, open a query with A, say something, and quit
  4. Start another session, connecting as nick C
  5. As nick C, open a query with A, say something, then issue a /nick B
  6. As B, open a query with A, say something
  7. In A's session, notice B's new query buffer is named B<2>

To put it another way: someone you have a query with disconnects and
reconnects under a new nick, perhaps due to their client appending a
backtick or an underscore. They then engage you in another query before
renicking to their original nick. Weechat and others deal with this by
reusing existing query buffers, but ERC has always added a uniquifying
suffix of the form A<2> to the new, renicked query buffer [1].

While it's true we can't technically be certain revived queries are
being piloted by the same individuals (at least not until ERC becomes
account aware), enough folks have complained about this over the years
that I think it's legitimate to disregard that uncertainty by default.
And though we're not obliged to address this for this release in
particular, I do think it's worth doing so soonish, especially given
that bug#48598 (ERC 5.5) was supposed to do away with these buffer
association issues. The second of the attached patches attempts to get
us closer to making good on that.

Thanks.

[1] Note that in the scenario above, attempting to "merge" buffers B and
    C, like ERC does after changing its own nick, may seem desirable,
    but it's tricky business because timelines may be interleaved rather
    than simply overlap at a single boundary interval. This is one of
    the many things a "backing store" or "replay" module could help
    solve, at least in cases brought about by unwanted backtick
    suffixing. A suitable back end would allow us to perform the merge
    in-store, perhaps ephemerally, and re-ingest it as clean, simulated
    input.


In GNU Emacs 30.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version
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Repository revision: 36c68e7e34df996bbde4cc82c04ea1619349b64a
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0001-5.6-Reconcile-erc-stamp-date-stamps-when-merging-buf.patch
Description: Text Data

0002-5.6-Reuse-old-query-buffers-for-round-trip-renicks-i.patch
Description: Text Data