https://lists.gnu.org/archive/html/emacs-devel/2026-02/msg00153.html

* lisp/progmodes/hideshow.el (hs-cycle-filter)
(hs-minor-mode-map): Update.
(hs--filter-function, hs-add-cycle-binding): New functions.
(hs-cycle): Minor rework.

Add explicit choice for the 0 value to always show the tab bar.
Also add a choice for other non-negative numbers.
In the setter enable 'tab-bar-mode' only for numbers,
but not for the t value that should not enable the tab bar
after customization, only after creating a new tab.

* lisp/emacs-lisp/package.el (package--delete-directory): Remove
manual before physically deleting the package.  (Bug#80776)

* lisp/subr.el (package--description-file): Do not expect
non-numeric version components to be followed directly by a
number.  (Bug#80744)

* lisp/emacs-lisp/package.el (package-status-obsolete): New face.
(package-menu-status-faces): Use new face instead of hard-coding
a font-lock face.

Define a short documentation group and document the major functions:

* lisp/calendar/icalendar-shortdoc.el: New file.
* lisp/calendar/diary-icalendar.el:
* lisp/calendar/icalendar-ast.el:
* lisp/calendar/icalendar-parser.el:
* lisp/calendar/icalendar-recur.el:
* lisp/calendar/icalendar-utils.el: Refer to icalendar-shortdoc.el in
file commentary.
* lisp/calendar/icalendar-macs.el: Ditto, and also mention the macros
for binding values.
* lisp/calendar/icalendar.el: Ditto, and also remove some obsolete
commentary.

Also make some improvements to documentation strings that the above
changes revealed would be helpful:

* lisp/calendar/icalendar-recur.el
(icalendar-recur-recurrences-in-window-w/end-times): Fix broken ref.
(icalendar-recur-current-tz-to-vtimezone): Clarify docstring.
* lisp/calendar/icalendar-parser.el (icalendar-parse): Clarify
docstring.

(Bug#80727)

As discussed in Bug#80520.

* test/lisp/calendar/icalendar-recur-tests.el
(icalendar-test-rrule-test-rfc5545-sec3.8.5.3/3)
(icalendar-test-rrule-test-rfc5545-sec3.8.5.3/29)
(icalendar-test-rrule-test-rfc5545-sec3.8.5.3/30)
(icalendar-test-rrule-test-rfc5545-sec3.8.5.3/31)
(icalendar-test-rrule-test-rfc5545-sec3.8.5.3/33)
(icalendar-test-rrule-test-rfc5545-sec3.8.5.3/34)
(icalendar-test-rrule-test-rfc5545-sec3.8.5.3/38): Mark tests expensive.

Abstract the implementation of intervals in icalendar-recur.el.  Don't
store interval NEXT-LOW when it's the same as HIGH.  This reduces
allocations, and shaves about ~20% off the full test suite.

* lisp/calendar/icalendar-recur.el
(icalendar-recur-make-interval)
(icalendar-recur-interval-low)
(icalendar-recur-interval-high)
(icalendar-recur-interval-next): Implement intervals and subintervals as
vectors.  Only store NEXT-LOW when it's non-nil.
(icalendar-recur-find-absolute-interval)
(icalendar-recur-find-daily-interval)
(icalendar-recur-find-weekly-interval)
(icalendar-recur-find-monthly-interval)
(icalendar-recur-find-yearly-interval)
(icalendar-recur-next-interval)
(icalendar-recur-previous-interval)
(icalendar-recur-refine-byyearday)
(icalendar-recur-refine-byweekno)
(icalendar-recur-refine-bymonth)
(icalendar-recur-refine-bymonthday)
(icalendar-recur-refine-byday)
(icalendar-recur-refine-byhour)
(icalendar-recur-refine-byminute)
(icalendar-recur-refine-bysecond)
(icalendar-recur-subintervals-to-date-times)
(icalendar-recur-subintervals-to-dates)
(icalendar-recur-recurrences-in-interval)
(icalendar-recur-recurrences-in-window)
(icalendar-recur--key-from-interval): Use new interval constructor and
accessors.  Don't generate NEXT-LOW when it's the same as HIGH.
* lisp/calendar/icalendar-utils.el (icalendar-dates-until): Use new
interval constructor and accessors.
* test/lisp/calendar/icalendar-recur-tests.el
(icalendar-test-recur-find-secondly-interval)
(icalendar-test-recur-find-minutely-interval)
(icalendar-test-recur-find-hourly-interval)
(icalendar-test-recur-find-daily-interval-w/date)
(icalendar-test-recur-find-daily-interval-w/date-time)
(icalendar-test-recur-find-weekly-interval-w/date)
(icalendar-test-recur-find-weekly-interval-w/date-time)
(icalendar-test-recur-find-monthly-interval)
(icalendar-test-recur-find-yearly-interval)
(icalendar-test-recur-refine-byyearday)
(icalendar-test-recur-refine-bymonth)
(icalendar-test-recur-refine-bymonthday)
(icalendar-test-recur-refine-byday)
(icalendar-test-recur-refine-byhour)
(icalendar-test-recur-refine-byminute)
(icalendar-test-recur-refine-bysecond)
(icalendar-test-recur-subintervals-to-dates)
(icalendar-test-recur-subintervals-to-date-times)
(icalendar-test-rrule-test): Use new interval constructor and accessors.

Rearrange loops when refining subintervals, so that the loop always runs
once but doesn't run a second no-op iteration.  Astonishingly this cuts
the running time of the full test suite by almost 50%.

* lisp/calendar/icalendar-recur.el (icalendar-recur-refine-byyearday)
(icalendar-recur-refine-byweekno)
(icalendar-recur-refine-bymonth)
(icalendar-recur-refine-bymonthday)
(icalendar-recur-refine-byday)
(icalendar-recur-refine-byhour)
(icalendar-recur-refine-byminute)
(icalendar-recur-refine-bysecond): Tighten up loop bounds when refining
subintervals.

Improve performance of `icalendar-recur-tz-observance-on'.  This also
brings about a ~20% performance gain.

* lisp/calendar/icalendar-recur.el
(icalendar-recur-tz-observance-on): Eliminate calculation of previous
interval recurrences when it's unnecessary.  Add a cheap upper bound check to
prevent fully computing recurrences for irrelevant observances.
(icalendar-recur--w/in-locally-p):
(icalendar-recur--w/in-abs-p): New helper functions for the upper bound check.

Other more minor changes:

Improve performance in `icalendar-recur-refine-byday'

* lisp/calendar/icalendar-recur.el (icalendar-recur-refine-byday): Avoid
calculating Gregorian from absolute date unless it's necessary.

Improve performance of BYSETPOS filtering in icalendar-recur.el:
η-reduce `icalendar-recur-make-bysetpos-filter'.
Thanks to Mattias Engdegård for the suggestion and implementation.

* lisp/calendar/icalendar-recur.el
(icalendar-recur-make-bysetpos-filter): Rename to
`icalendar-recur-bysetpos-filter' and avoid `seq-map-indexed'.
(icalendar-recur-recurrences-in-interval): Use new function.
* test/lisp/calendar/icalendar-recur-tests.el
(icalendar-test-recur-bysetpos-filter): Use new function.

Improve sorting performance:
Thanks to Mattias Engdegård for the suggestion and implementation.

* lisp/calendar/icalendar-recur.el (icalendar-recur-refine-byyearday):
(icalendar-recur-refine-byweekno):
(icalendar-recur-refine-bymonthday):
(icalendar-recur-refine-byday): Use :key instead of :lessp in `sort'
calls.

Eliminate `apply-partially' and `seq-take':
Thanks to Mattias Engdegård for the suggestion and implementation.

* lisp/calendar/icalendar-recur.el
(icalendar-recur-recurrences-in-window): Eliminate `apply-partially'.
(icalendar-recur-recurrences-in-interval): Eliminate
`apply-partially' and replace `seq-take' with `take'.

Reduce consing:

* lisp/calendar/icalendar-recur.el
(icalendar-recur-subintervals-to-dates):
(icalendar-recur-recurrences-in-window):
(icalendar-recur-recurrences-in-window-w/end-times):
(icalendar-recur-recurrences-to-count): Replace `append' with `nconc'.

Avoid a few uses of `seq-filter' in common functions in icalendar-ast.el:

* lisp/calendar/icalendar-ast.el (icalendar-ast-node-children-of):
Reimplement filter imperatively.

* src/w32console.c (syms_of_ntterm) <w32--terminal-is-conhost>:
New variable.
(initialize_w32_display): Set 'w32--terminal-is-conhost' non-nil
when running on ConHost.

* lisp/international/characters.el (use-cjk-char-width-table):
When Emacs runs on MS-Windows Terminal, behave as if
'cjk-ambiguous-chars-are-wide' were nil even in CJK locales.
(Bug#79298)