* lisp/so-long.el: (so-long-statistics-excessive-p): New predicate
function using `buffer-line-statistics'.
(so-long-predicate): Use `so-long-statistics-excessive-p' by default.

* etc/NEWS: Describe changes.

* test/lisp/so-long-tests/so-long-tests-helpers.el:
* test/lisp/so-long-tests/so-long-tests.el: Update tests.
Also improve the existing `so-long-tests-predicate' tests.

The default values support preserving the state of `view-mode' when
switching to (and reverting from) `so-long-mode' (bug#45084).

* lisp/so-long.el (so-long-mode-preserved-variables)
(so-long-mode-preserved-minor-modes): New user options.
(so-long-mode-maintain-preserved-variables)
(so-long-mode-maintain-preserved-minor-modes): New functions.
(so-long-remember-all, so-long-after-change-major-mode)
(so-long-mode-revert): Use them.

* etc/NEWS: Describe changes.

* test/lisp/so-long-tests/so-long-tests-helpers.el:
* test/lisp/so-long-tests/so-long-tests.el: Update tests.

* test/lisp/so-long-tests/so-long-tests.el
(so-long-tests-invisible-buffer-function): Suppress warning about
obsolete function `run-window-configuration-change-hook', as we are
using it intentionally (see the preceding code comments and URL for
details).

(so-long-disable-minor-modes): Don't call the mode function to disable
the mode unless it was actually enabled.

(so-long-restore-minor-modes, so-long-restore-variables): Use the
remembered list values, which might be different to the defaults.

Also comments, and spelling consistency changes for the so-long tests
(a fixup for commit 83bc4ad369 which had only addressed so-long.el,
and not the test files).

* test/lisp/autorevert-tests.el: Mark all tests as unstable on
Cygwin (bug#49665).

Reported by Gregor Zattler.

* lisp/emacs-lisp/bytecomp.el (byte-compile--cond-switch-prefix):
Be more careful in the selection of equality.
* test/lisp/emacs-lisp/bytecomp-tests.el (bytecomp-tests--test-cases):
Add test case.

* lisp/net/tramp-sh.el (tramp-do-copy-or-rename-file):
* lisp/net/tramp-sudoedit.el (tramp-sudoedit-do-copy-or-rename-file):
Remove compat code for `{set-}file-extended-attributes'.
(tramp-sudoedit-handle-write-region): Handle extended attributes.
(Bug#49724)

* test/lisp/net/tramp-tests.el (tramp-test25-file-selinux):
Fix test for sudoedit method.

Use the `occur-target` text property to keep track of the extents of
all matches on each line instead of just the start of the first match.
Doing so allows us to highlight all matches when jumping to a matching
line instead of just the first one, and it works in a more principled
way.  It also removes compatibility problems that were introduced with
occur-highlight-regexp.

For compatibility with code that populate their own occur-mode
buffers, we still accept `occur-target` properties with a single
marker as value.

* lisp/replace.el (occur-highlight-regexp, occur-highlight-overlay):
Remove.
(occur-highlight-overlays): New.
(occur--targets-start): New.
* lisp/replace.el (occur-after-change-function):
(occur-mode-find-occurrence): Replace with...
(occur-mode--find-occurrences): ...this function that returns the
whole `occur-target` property value.
(occur-mode-goto-occurrence, occur-mode-goto-occurrence-other-window)
(occur-goto-locus-delete-o, occur-mode-display-occurrence)
(occur-engine): Adjust to new property format.
(occur--highlight-occurrence): Replace with...
(occur--highlight-occurrences): ...this function that takes
the `occur-target` property value as argument.
(occur-1): Don't use `occur-highlight-regexp`.
* test/lisp/replace-tests.el (occur-highlight-occurrence):
Adapt to new property format.

* src/fileio.c (Ffile_name_concat):
* lisp/files.el (move-file-to-trash):
* lisp/emacs-lisp/shortdoc.el (file-name):
* doc/lispref/files.texi (Directory Names): Rename
`directory-append' to `file-name-concat'.

* doc/lispref/files.texi (Directory Names): Document it.
* src/fileio.c (Fdirectory_append): Allow empty elements.