bug#56450: 29.0.50; erc-match commands should store regular expressions

[J.P.]

Tags: patch

Currently, pals, fools, keywords, etc. aren't `regexp-quote'd by their
associated commands (such as `erc-add-pal') before being added as match
patterns. Thus, items containing special characters, like "boo[m]" or
"lol.fun.dad", tend to be ineffective. Worse, invalid regexps containing
things like unmatched brackets create errors in the process filter.

Something else not included that perhaps should be is a clearer
indication that items added interactively can match any substring in a
candidate without regard for boundaries. It may also be worth
contrasting this with what's ultimately highlighted. For example, if you
"M-x erc-add-pal RET bo RET", then "<bob>" (minus the brackets) will be
highlighted. Compare this to keywords, where only the matched portion
appears in a designated face.

Documentation aside, it might also be nice to retain a means of
interactively adding a regexp verbatim (IOW, the old behavior minus the
unhelpful completion list). Perhaps this can be done via universal
argument.

BTW, the individual who originally brought this to our attention on
Libera also mused about a command for jumping between keywords, so I've
included something sketchy to that effect. However, it suffers from an
intermittent issue that I can't yet reproduce reliably: basically, when
first invoked, it sometimes makes Emacs unresponsive for a few seconds.
If I can't manage to tame it, I'll just drop it from this patch set.

Lastly, these changes (as presented) uphold the proud ERC tradition of
mutating custom options on behalf of a user. If this is truly
objectionable, then I can switch to network-local analogs instead.
However, such a move may adversely affect third-party code, given that
this module's been around in roughly the same form for some 20 odd
years.

Thanks,
J.P.

P.S. This bug is not (yet) associated with any planned ERC release.


In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.34, cairo 
version 1.17.6)
 of 2022-07-06 built on localhost
Repository revision: e6504c3eda12c72268d2db6598764f043b74c24d
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Fedora Linux 36 (Workstation Edition)

Configured using:
 'configure --enable-check-lisp-object-type --enable-checking=yes,glyphs
 'CFLAGS=-O0 -g3'
 PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

Configured features:
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JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
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TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
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Major mode: Lisp Interaction

Minor modes in effect:
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Load-path shadows:
None found.

Features:
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Memory information:
((conses 16 35545 5688)
 (symbols 48 5073 0)
 (strings 32 13303 1546)
 (string-bytes 1 429956)
 (vectors 16 9197)
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0001-Quote-new-entries-as-regexps-in-erc-match-commands.patch
Description: Text Data

0002-Add-command-to-jump-to-erc-match-keywords.patch
Description: Text Data