* doc/lispref/abbrevs.texi (Abbrev Tables):
* doc/lispref/symbols.texi (Creating Symbols):
* doc/lispref/objects.texi (Type Predicates): Update text for obarray
now being an opaque type.
* etc/NEWS: Announce.

The new opaque type replaces the previous use of vectors for obarrays.
`obarray-make` now returns objects of this type.  Functions that take
obarrays continue to accept vectors for compatibility, now just using
their first slot to store an actual obarray object.

obarray-size and obarray-default-size now obsolete.

* lisp/obarray.el (obarray-default-size, obarray-size):
Declare obsolete.
(obarray-make, obarrayp, obarray-clear): Remove from here.
* src/fns.c (reduce_emacs_uint_to_hash_hash): Remove from here.
* src/lisp.h (struct Lisp_Obarray, OBARRAYP, XOBARRAY, CHECK_OBARRAY)
(make_lisp_obarray, obarray_size, obarray_bucket, check_obarray)
(obarray_iter_t, make_obarray_iter, obarray_iter_at_end)
(obarray_iter_step, obarray_iter_symbol, DOOBARRAY, knuth_hash): New.
(reduce_emacs_uint_to_hash_hash): Moved here.
* src/lread.c (check_obarray): Renamed and reworked as...
(checked_obarray_slow): ...this.
(intern_sym, Funintern, oblookup, map_obarray)
(Finternal__obarray_buckets): Adapt to new type.
(obarray_index, allocate_obarray, make_obarray, grow_obarray)
(obarray_default_bits, Fobarray_make, Fobarrayp, Fobarray_clear): New.
* etc/emacs_lldb.py (Lisp_Object):
* lisp/emacs-lisp/cl-macs.el (`(,type . ,pred)):
* lisp/emacs-lisp/cl-preloaded.el (cl--typeof-types):
* lisp/emacs-lisp/comp-common.el (comp-known-type-specifiers):
* lisp/emacs-lisp/comp.el (comp-known-predicates):
* src/alloc.c (cleanup_vector, process_mark_stack):
* src/data.c (Ftype_of, syms_of_data):
* src/minibuf.c (Ftry_completion, Fall_completions, Ftest_completion):
* src/pdumper.c (dump_obarray_buckets, dump_obarray, dump_vectorlike):
* src/print.c (print_vectorlike_unreadable):
* test/lisp/abbrev-tests.el (abbrev-make-abbrev-table-test):
* test/lisp/obarray-tests.el (obarrayp-test)
(obarrayp-unchecked-content-test, obarray-make-default-test)
(obarray-make-with-size-test):
Adapt to new type.

* lisp/epa.el (epa-keys-select-method): New defcustom.
(epa--select-keys-in-minibuffer): New function.
(epa-select-keys): Use new option and function.
* etc/NEWS: Announce it.
* doc/misc/epa.texi (Key Management): Document it.
(Bug#69133)

* etc/ERC-NEWS: Mention `erc-open' now ignores TGT-LIST.
* lisp/erc/erc.el (erc-open): Set `erc-default-recipients' to a list
containing only the supplied target.  Other values may cause ERC to
malfunction.  Also redo doc string.

* lisp/ielm.el (inferior-emacs-lisp-mode): Add support for saving input
history to a file.
(ielm--history-file-name): New variable indicating IELM input history
file.
(ielm--exit): Holds a function to call when Emacs is killed to write
out the input history.
(ielm--input-history-writer): Helper function for writing the IELM
input history out to file.

* lisp/comint.el (comint-input-ring-file-name): Improve defcustom tag.

Add a `tit-` or `tit--` prefix where necessary.  Adjust all callers.
I kept the old names via obsolete aliases for now, although it's probably not
worth the trouble.

* lisp/international/titdic-cnv.el: Bring all definitions under the
`tit-` namespace.
(tit-quail-cxterm-package-ext-info): Rename var from
`quail-cxterm-package-ext-info`.  Adjust value to new names.
(tit-dic-convert): Rename from `titdic-convert`.
(batch-tit-dic-convert): Rename from `batch-titdic-convert`.
(tit-quail-misc-package-ext-info): Rename var from
`quail-misc-package-ext-info`.  Adjust value to new names.
(tit--tsang-quick-converter): Rename from `tsang-quick-converter`.
(tit--tsang-b5-converter): Rename from `tsang-b5-converter`.
(tit--quick-b5-converter): Rename from `quick-b5-converter`.
(tit--tsang-cns-converter): Rename from `tsang-cns-converter`.
(tit--quick-cns-converter): Rename from `quick-cns-converter`.
(tit--py-converter): Rename from `py-converter`.
(tit--ziranma-converter): Rename from `ziranma-converter`.
(tit--ctlau-converter): Rename from `ctlau-converter`.
(tit--ctlau-gb-converter): Rename from `ctlau-gb-converter`.
(tit--ctlau-b5-converter): Rename from `ctlau-b5-converter`.
(tit-miscdic-convert): Rename from `miscdic-convert`.
(batch-tit-miscdic-convert): Rename from `batch-miscdic-convert`.
(tit-pinyin-convert): Rename from `pinyin-convert`.

* leim/Makefile.in (${leimdir}/quail/%.el, misc_convert)
(${srcdir}/../lisp/language/pinyin.el): Use the new names.

* lisp/cus-edit.el (customize-toggle-option): Add command.
(toggle-option): Add shorter alias for 'customize-toggle-option'.
* etc/NEWS: Document it.  (Bug#69079)

* doc/emacs/text.texi (Outline Format): Add 'outline-search-function'.

* doc/lispref/elisp.texi (Top): Add new menu item "Outline Minor Mode"
after "Imenu".

* doc/lispref/modes.texi (Modes): Add new menu item "Outline Minor Mode"
after "Imenu".
(Major Mode Conventions): Mention "Outline Minor Mode" with @pxref.
(Outline Minor Mode): New node.

* doc/lispref/parsing.texi (Tree-sitter Major Modes): Mention
'treesit-outline-predicate' with @pxref.

* lisp/treesit.el (treesit-outline-predicate): New buffer-local variable.
(treesit-outline-predicate--from-imenu): New internal function.
(treesit-outline-search, treesit-outline-level): New functions.
(treesit-major-mode-setup): Set up treesit-outline-predicate,
outline-search-function and outline-level.

* lisp/progmodes/c-ts-mode.el (c-ts-mode--outline-predicate):
New internal function.
(c-ts-base-mode): Set 'treesit-outline-predicate' to
'c-ts-mode--outline-predicate'.

* lisp/progmodes/heex-ts-mode.el (heex-ts-mode): Kill inherited
local variables 'outline-heading-end-regexp', 'outline-regexp',
'outline-level'.

* lisp/progmodes/lua-ts-mode.el (lua-ts-mode): Remove 'outline-regexp'.
Suggested by john muhl <jm@pub.pink>.

* lisp/textmodes/html-ts-mode.el (html-ts-mode): Kill inherited
local variables 'outline-heading-end-regexp', 'outline-regexp',
'outline-level'.

The current syntax for functions in `app` and `pred` patterns
allows a shorthand (F ARGS) where the object being matched is
added as an extra last argument.  This is nice for things like
(pred (< 5)) but sometimes the object needs to be at
another position.
Until now you had to use (pred (lambda (x) (memq x my-list)))
or (pred (pcase--flip memq my-list)) in those cases.
So, introduce a new shorthand where `_` can be used to indicate
where the object should be passed: (pred (memq _ my-list))

* lisp/emacs-lisp/pcase.el (pcase--split-pred): Document new syntax
for pred/app functions.
(pcase--funcall): Support new syntax.
(pcase--flip): Declare obsolete.
(pcase--u1, \`): Use `_` instead.
(pcase--split-pred): Adjust accordingly.

* doc/lispref/control.texi (pcase Macro): Document new syntax
for pred/app functions.

* lisp/progmodes/opascal.el (pcase-defmacro):
* lisp/emacs-lisp/seq.el (seq--make-pcase-bindings):
* lisp/emacs-lisp/eieio.el (eieio):
* lisp/emacs-lisp/cl-macs.el (cl-struct, cl-type):
Use _ instead of `pcase--flip`.
(cl--pcase-mutually-exclusive-p): Adjust accordingly.

* lisp/emacs-lisp/map.el (map--pcase-map-elt): Declare obsolete.
(map--make-pcase-bindings): Use `_` instead.

* lisp/emacs-lisp/compat.el: Add stub file with minimal definitions,
so that core packages, that haven't been installed from ELPA, can make
use of the public API and use more recent function signatures.
* lisp/progmodes/python.el (compat): Remove 'noerror flag, because
Compat can now be required without the real package being available.
* doc/lispref/package.texi (Forwards-Compatibility): Mention Compat
and link to the manual.
* etc/NEWS: Document change.  (Bug#66554)