* lisp/eshell/esh-ext.el (eshell-explicit-remote-commands)
(eshell-explicit-command): Update docstrings.
(eshell--local-prefix): New constant.
(eshell-handle-remote-command): Remove.
(eshell-quoted-file-command): New function...
(eshell-ext-initialize): ... add it as a hook.
(eshell-remote-command): Support running commands on localhost.
(eshell-connection-local-command): Rename from
'eshell-external-command'.
(eshell-external-command): New implementation calling
'eshell-remote-command' or 'eshell-connection-local-command' as
appropriate.
* test/lisp/eshell/esh-ext-tests.el
(esh-ext-test/explicitly-local-command): Update test.
* doc/misc/eshell.texi (Remote Access): Update documentation.
* etc/NEWS: Update announcement.
* lisp/files.el (file-remote-p):
* doc/lispref/files.texi (Magic File Names): Document 'never' for
CONNECTED argument.
* lisp/net/tramp.el (tramp-handle-file-remote-p): Handle CONNECTED
value of 'never'.
* lisp/eshell/esh-ext.el (eshell-explicit-remote-commands): New
option.
(eshell-ext-initialize): Apply 'eshell-handle-remote-command' when
requested.
(eshell-handle-remote-command): New function.
(eshell-remote-command): Reimplement this function and dispatch to
'eshell-external-command', which can handle remote processes on its
own.
* test/lisp/eshell/esh-ext-tests.el
(esh-ext-test/explicitly-remote-command)
(esh-ext-test/explicitly-local-command): New tests.
* doc/misc/eshell.texi (Remote Access): Document explicitly-remote
commands.
* etc/NEWS: Announce this change.
* lisp/eshell/esh-util.el (eshell-path-env, eshell-parse-colon-path):
Make obsolete.
(eshell-path-env-list): New variable.
(eshell-connection-default-profile): New connection-local profile.
(eshell-get-path): Reimplement using 'eshell-path-env-list'; add
LITERAL-P argument.
(eshell-set-path): New function.
* lisp/eshell/esh-var.el (eshell-variable-aliases-list): Add entry for
$PATH.
(eshell-var-initialize): Add 'eshell-path-env-list' to
'eshell-subcommand-bindings'.
* lisp/eshell/esh-ext.el (eshell-search-path): Use 'file-name-concat'
instead of 'concat'.
(eshell/addpath): Use 'eshell-get-path' and 'eshell-set-path'.
* lisp/net/tramp-integration.el: Only apply Eshell hooks when
'eshell-path-env-list' is unbound.
* test/lisp/eshell/esh-var-tests.el
(esh-var-test/path-var/local-directory)
(esh-var-test/path-var/remote-directory, esh-var-test/path-var/set)
(esh-var-test/path-var/set-locally)
(esh-var-test/path-var-preserve-across-hosts): New tests.
* test/lisp/eshell/esh-ext-tests.el: New file.
* test/lisp/eshell/eshell-tests-helpers.el
(with-temp-eshell): Set 'eshell-last-dir-ring-file-name' to nil.
(eshell-tests-remote-accessible-p, eshell-last-input)
(eshell-last-output): New functions.
(eshell-match-output, eshell-match-output--explainer): Use
'eshell-last-input' and 'eshell-last-output'.
* doc/misc/eshell.texi (Variables): Document $PATH.
* etc/NEWS: Announce this change (bug#57556).
