* lisp/net/tramp-adb.el (tramp-adb-handle-exec-path):
* lisp/net/tramp-sh.el (tramp-sh-handle-exec-path): Use ´file-remote-p'.
(tramp-get-ls-command-with): Handle busybox specially.

* test/lisp/net/tramp-tests.el (tramp-test34-exec-path): Check for
`fboundp'.  Use `file-remote-p'.  Hide compiler warning for older
Emacsen.

* doc/lispref/files.texi (Locating Files): Describe optional
argument REMOTE of `executable-find'.
(Magic File Names): Add `exec-path'.

* doc/lispref/processes.texi (Subprocess Creation): Describe
function `exec-path'.

* doc/misc/tramp.texi (Remote programs): Explain refresh of search
paths by `tramp-cleanup-this-connection'.

* etc/NEWS: Mention 'exec-path' and 'executable-find'.

* lisp/files.el (exec-path): New defun.
(executable-find): Add optional argument REMOTE.

* lisp/shell.el (shell-completion-vars): Set `comint-file-name-prefix'.
(shell--command-completion-data): Use `(exec-path)'.  (Bug#31704)

* lisp/net/ange-ftp.el (exec-path):
* lisp/net/tramp.el (tramp-file-name-for-operation):
* lisp/net/tramp-adb.el (tramp-adb-file-name-handler-alist):
* lisp/net/tramp-archive.el (tramp-archive-file-name-handler-alist):
* lisp/net/tramp-gvfs.el (tramp-gvfs-file-name-handler-alist):
* lisp/net/tramp-sh.el (tramp-sh-file-name-handler-alist):
* lisp/net/tramp-smb.el (tramp-smb-file-name-handler-alist)
<exec-path>: Add handler.

* lisp/net/tramp-adb.el (tramp-adb-handle-exec-path): New defun.
(tramp-adb-maybe-open-connection): Do not set "remote-path"
connection property.

* lisp/net/tramp-compat.el (tramp-compat-exec-path): New defun.

* lisp/net/tramp-sh.el (tramp-sh-handle-exec-path): New defun.

* lisp/net/tramp.el (tramp-eshell-directory-change): Use it.

* test/lisp/net/tramp-archive-tests.el
(tramp-archive-test38-make-nearby-temp-file)
(tramp-archive-test41-file-system-info)
(tramp-archive-test43-auto-load)
(tramp-archive-test43-delay-load): Rename.

* test/lisp/net/tramp-tests.el (tramp-test34-exec-path): New test.
(tramp-test36-make-auto-save-file-name)
(tramp-test37-find-backup-file-name)
(tramp-test38-make-nearby-temp-file)
(tramp-test39-special-characters)
(tramp-test39-special-characters-with-stat)
(tramp-test39-special-characters-with-perl)
(tramp-test39-special-characters-with-ls, tramp-test40-utf8)
(tramp-test40-utf8-with-stat, tramp-test40-utf8-with-perl)
(tramp-test40-utf8-with-ls, tramp-test41-file-system-info)
(tramp-test42-asynchronous-requests, tramp-test43-auto-load)
(tramp-test43-delay-load, tramp-test43-recursive-load)
(tramp-test43-remote-load-path, tramp-test44-unload): Rename.

* test/lisp/net/secrets-tests.el (secrets-test03-items)
(secrets-test04-search): Cleanup "session" collection initially.

* lisp/files.el (insert-file-contents-literally):
Bind `inhibit-file-name-handlers' the default way.
(file-name-non-special): Rework, mainly for operations with two
file name arguments.
(file-name-unquote-non-special): New defsubst.
(file-name-unquote): Use it.

* test/lisp/files-tests.el (files-test-bug-18141): Skip if needed.
(files-tests--with-temp-non-special): Add docstring.  Delete also
`non-special-name' if the file/directory exists.
(files-tests--special-file-name-extension)
(files-tests--special-file-name-regexp): New defconst.
(files-tests--special-file-name-handler, files-tests--new-name):
New defuns.
(files-tests--with-temp-non-special-and-file-name-handler): New macro.
(files-tests-file-name-non-special-access-file)
(files-tests-file-name-non-special-add-name-to-file)
(files-tests-file-name-non-special-byte-compiler-base-file-name)
(files-tests-file-name-non-special-copy-directory)
(files-tests-file-name-non-special-copy-file)
(files-tests-file-name-non-special-delete-directory)
(files-tests-file-name-non-special-delete-file)
(files-tests-file-name-non-special-diff-latest-backup-file)
(files-tests-file-name-non-special-directory-file-name)
(files-tests-file-name-non-special-directory-files)
(files-tests-file-name-non-special-directory-files-and-attributes)
(files-tests-file-name-non-special-dired-compress-handler)
(files-tests-file-name-non-special-dired-uncache)
(files-tests-file-name-non-special-expand-file-name)
(files-tests-file-name-non-special-file-accessible-directory-p)
(files-tests-file-name-non-special-file-acl)
(files-tests-file-name-non-special-file-attributes)
(files-tests-file-name-non-special-file-directory-p)
(files-tests-file-name-non-special-file-equal-p)
(files-tests-file-name-non-special-file-executable-p)
(files-tests-file-name-non-special-file-exists-p)
(files-tests-file-name-non-special-file-in-directory-p)
(files-tests-file-name-non-special-file-local-copy)
(files-tests-file-name-non-special-file-modes)
(files-tests-file-name-non-special-file-name-all-completions)
(files-tests-file-name-non-special-file-name-as-directory)
(files-tests-file-name-non-special-file-name-case-insensitive-p)
(files-tests-file-name-non-special-file-name-completion)
(files-tests-file-name-non-special-file-name-directory)
(files-tests-file-name-non-special-file-name-nondirectory)
(files-tests-file-name-non-special-file-name-sans-versions)
(files-tests-file-name-non-special-file-newer-than-file-p)
(files-tests-file-name-non-special-notify-handlers)
(files-tests-file-name-non-special-file-ownership-preserved-p)
(files-tests-file-name-non-special-file-readable-p)
(files-tests-file-name-non-special-file-regular-p)
(files-tests-file-name-non-special-file-remote-p)
(files-tests-file-name-non-special-file-selinux-context)
(files-tests-file-name-non-special-file-symlink-p)
(files-tests-file-name-non-special-file-truename)
(files-tests-file-name-non-special-file-writable-p)
(files-tests-file-name-non-special-find-backup-file-name)
(files-tests-file-name-non-special-get-file-buffer)
(files-tests-file-name-non-special-insert-directory)
(files-tests-file-name-non-special-insert-file-contents)
(files-tests-file-name-non-special-load)
(files-tests-file-name-non-special-make-auto-save-file-name)
(files-tests-file-name-non-special-make-directory)
(files-tests-file-name-non-special-make-directory-internal)
(files-tests-file-name-non-special-make-symbolic-link)
(files-tests-file-name-non-special-rename-file)
(files-tests-file-name-non-special-set-file-acl)
(files-tests-file-name-non-special-set-file-modes)
(files-tests-file-name-non-special-set-file-selinux-context)
(files-tests-file-name-non-special-set-file-times)
(files-tests-file-name-non-special-set-visited-file-modtime)
(files-tests-file-name-non-special-shell-command)
(files-tests-file-name-non-special-start-file-process)
(files-tests-file-name-non-special-substitute-in-file-name)
(files-tests-file-name-non-special-temporary-file-directory)
(files-tests-file-name-non-special-unhandled-file-name-directory)
(files-tests-file-name-non-special-vc-registered)
(files-tests-file-name-non-special-write-region): Extends tests to
quoted file names, which would require a file name handler if unquoted.
(files-test-no-file-write-contents): Make test more robust.

* test/lisp/net/tramp-tests.el (tramp-test21-file-links): Adapt test.
(tramp--test-emacs25-p): New defun.
(tramp-test34-vc-registered): Use it.

* lisp/net/tramp.el (tramp-handle-file-name-directory): Fix case
of localname starts w/o a slash.

* test/lisp/net/tramp-tests.el (tramp-test06-directory-file-name):
Extend test.

* lisp/net/secrets.el (secrets-search-item-paths): New function.
(secrets-search-items): Use it.
(secrets-create-item): Adapt docstring.

* test/lisp/net/secrets-tests.el (secrets-test04-search): Extend test.

* doc/misc/tramp.texi (Frequently Asked Questions):
Mention `tramp-ignored-file-name-regexp'.  Improve index.

; * etc/NEWS: Mention `tramp-ignored-file-name-regexp'.

* lisp/net/tramp.el (tramp-ignored-file-name-regexp): New defcustom.
(tramp-tramp-file-p): Use it.  Check also for `tramp-mode'.
(tramp-file-name-handler): Don't check for `tramp-mode'.  (Bug#31489)

* test/lisp/net/tramp-tests.el (tramp-test01-file-name-syntax):
Extend test.

* lisp/auth-source.el (auth-source-secrets-create): Use ´apply'.
(auth-source-secrets-saver): Handle `auth-source-save-behavior'
equal t.

* lisp/net/secrets.el (secrets-get-items): Do not call
`secrets-open-session' here ...
(top): ... but here.

* test/lisp/auth-source-tests.el
(auth-source-test-secrets-create-secret): Bind
`auth-source-save-behavior' to t.  Cleanup.

* test/lisp/net/secrets-tests.el (secrets-test00-availability):
After loading secets.el, a session is already opened.
(secrets-test02-collections, secrets-test03-items)
(secrets-test04-search): Open a new session.

* lisp/net/secrets.el (secrets-create-item): The new item does not
need a unique label.
(secrets-item-path, secrets-get-secret, secrets-get-attributes)
(secrets-get-attribute, secrets-delete-item): ITEM can also be an
object path.  (Bug#29575)

* test/lisp/net/secrets-tests.el (secrets-test03-items):
Test also creation of two items with same label.  Test
`secrets-get-secret', `secrets-get-attribute' and
`secrets-get-attributes' with object path.
(secrets-test04-search): Harden test.

* lisp/net/tramp-gvfs.el (tramp-gvfs-handle-file-attributes):
Parse multibyte symlinks correctly.

* test/lisp/net/tramp/tramp-tests.el (tramp--test-utf8):
Improve backward compatibility.