* lisp/misc.el (duplicate-region-final-position): New defcustom.
(duplicate-dwim): Use it.
* lisp/rect.el (rectangle--duplicate-right): Add displacement
argument.
* test/lisp/misc-tests.el (misc--duplicate-dwim): Extend test.

* lisp/misc.el (duplicate-line): Use it.

* test/lisp/misc-tests.el (misc--duplicate-line): Add tests for
duplicate-line-final-position.

Like duplicate-line but duplicates the region instead if active.
Rectangular regions are duplicated on the right-hand side.
The region remains active afterwards, to facilitate further
duplication or other operations on the same text.

* lisp/rect.el (rectangle--duplicate-right):
* lisp/misc.el (duplicate-dwim): New.
* test/lisp/misc-tests.el (misc--duplicate-dwim): New test.
* etc/NEWS: Announce.

The test assumes that the current semantics are intended and desired,
which may or may not be true, but it's better than not having any at
all.

* lisp/misc.el (duplicate-line): Don't crash if called with no argument.
* test/lisp/misc-tests.el (misc--duplicate-line): New test.

In interactive calls, behave case-sensitively if the given char
is an upper-case character.  Same for zap-up-to-char (Bug#54804).

This is analog to what the user-level incremental search feature does.

* lisp/misc.el (zap-up-to-char): Add an optional arg INTERACTIVE.
Perform a case-sensitive search when INTERACTIVE is non-nil and
CHAR is an upper-case character.
* lisp/simple.el (zap-to-char): Same.

* etc/NEWS (Editing Changes in Emacs 29.1): Announce this change.
* test/lisp/misc-tests.el (misc-test-zap-up-to-char): Add test cases.
* test/lisp/simple-tests.el (with-zap-to-char-test): Add helper macro.
(simple-tests-zap-to-char): Add a test.

Run "TZ=UTC0 admin/update-copyright".

* lisp/misc.el: Use lexical-binding.
* test/lisp/misc-tests.el: New file.