* lisp/eshell/esh-proc.el (eshell-gather-process-output): Get the
local part of the $PATH (bug#67126).

Copyright-paperwork-exempt: yes

* lisp/eshell/em-hist.el (eshell-hist--new-items): New variable.
(eshell-hist-initialize): Initialize 'eshell-hist--new-items' to 0.
(eshell/history): Change the behavior of 'history -a' to "append new
history in current buffer to history file".  Clarify the help text of
'history -r'.
(eshell-add-input-to-history): Increase counter of new history items.
(eshell-read-history): Respect 'eshell-hist-ignoredups' option.
(eshell-write-history): If the optional argument APPEND is non-nil,
appending new history items rather than the whole history.

* test/lisp/eshell/em-hist-tests.el (em-hist-test/history-append)
(em-hist-test/history-read): New tests (bug#66768).

em-smart was forcibly re-displaying the screen upwards of 500 times
per screen of output.  This caused the Eshell to feel quite slow when
the module was in use.  By using fewer hooks and never explicitly
calling 'redisplay' (which was unnecessary) the performance issues go
away (bug#57367).

lisp/eshell/em-smart.el:

(em-smart-unload-hook, eshell-smart-unload-hook): Remove
'eshell-smart-scroll' instead of the now deleted
'eshell-refresh-windows'.

(eshell-smart-displayed, eshell-currently-handling-window)
(eshell-refresh-windows): Delete.

(eshell-smart-scroll-window): Rename to 'eshell-smart-scroll-windows'
and add a bunch of logic originally from 'eshell-refresh-windows'.

(eshell-smart-initialize): Don't add a hook onto
'window-scroll-functions'.  Replace 'eshell-refresh-windows' with
'eshell-smart-scroll-windows'.

(eshell-smart-display-setup): Don't refresh windows.

(eshell-smart-redisplay): Rename to 'eshell-smart-scroll'.  Delete
'eobp' case.

* lisp/eshell/esh-arg.el (eshell-get-marker, eshell-insert-marker)
(eshell-complete-marker-ref): New functions...
(eshell-special-ref-alist): ... Add them to the new "marker" entry.

* test/lisp/eshell/esh-arg-tests.el
(esh-arg-test/special-reference/marker)
(esh-arg-test/special-reference/nested)
(esh-arg-test/special-reference/lisp-form):
* test/lisp/eshell/em-cmpl-tests.el
(em-cmpl-test/special-ref-completion/type)
(em-cmpl-test/special-ref-completion/marker): New tests.

* doc/misc/eshell.texi (Arguments): Document the new special ref type.

* etc/NEWS: Announce this change (bug#66458).

* lisp/eshell/esh-cmd.el (eshell--region-p, eshell-with-temp-command):
Move to...
* lisp/eshell/esh-util.el (eshell--region-p)
(eshell-with-temp-command): ... here.

* lisp/eshell/em-cmpl.el (eshell-complete-parse-arguments): Fix edge
case when 'end' is at beginning of (possibly-narrowed) buffer.

* lisp/eshell/esh-arg.el (eshell-special-ref-alist) New variable...
(eshell-special-ref-default): ... New option...
(eshell--special-ref-function): ... New function...
(eshell-parse-special-reference): ... use them.
(eshell-insert-special-reference): New function.
(eshell-complete-special-reference): Reimplement to use a nested call
to Pcomplete.
(eshell-complete-buffer-ref): New function.

* lisp/eshell/esh-proc.el (eshell-proc-initialize): Add "process"
special ref type here.
(eshell-complete-process-ref): New function.

* doc/misc/eshell.texi (Bugs and ideas): Remove now-implemented idea.

* lisp/eshell/esh-arg.el (eshell-current-argument-plain): New variable.
(eshell-parse-special-reference): Use 'eshell-parse-arguments'.
(eshell-get-buffer): New function.
(eshell-insert-buffer-name): Properly quote the buffer name.

* lisp/eshell/esh-proc.el (eshell-read-process-name): Move to "Special
references" section.
(eshell-insert-process): Properly quote the process name.

* lisp/eshell/em-extpipe.el (eshell-parse-external-pipeline):
* lisp/eshell/esh-io.el (eshell-parse-redirection): Don't do anything
when 'eshell-argument-plain' is non-nil.

* test/lisp/eshell/esh-arg-tests.el
(esh-arg-test/special-reference/quoted)
(esh-arg-test/special-reference/var-expansion): New tests.
(esh-arg-test/special-reference/special): Rename to...
(esh-arg-test/special-reference/special-characters): ... this.

* test/lisp/eshell/em-extpipe-tests.el (em-extpipe-tests--deftest):
Properly quote the buffer name.
(em-extpipe-test-4, em-extpipe-test-7): Use 'eshell-get-buffer'.

* lisp/eshell/esh-proc.el (eshell-kill-process-wait-time): Update type.

* lisp/eshell/esh-proc.el (eshell-process-wait-seconds)
(eshell-process-wait-milliseconds): Make obsolete in favor of...
(eshell-process-wait-time): ... this, and...
(eshell-wait-for-process): ... use it.

* etc/NEWS: Announce this change (bug#66574).

This fixes a small regression from commit eef32d13da5.

* lisp/eshell/esh-proc.el (eshell-reset): Declare here.
(eshell-reset-after-proc): Move implementation to...
(eshell--reset-after-signal): ... here...
(eshell-interrupt-process, eshell-kill-process eshell-quit-process)
(eshell-stop-process, eshell-continue-process): ... and call it.