Add Tramp option showing ad-hoc multi-hops

* doc/misc/tramp.texi (Ad-hoc multi-hops):
Describe tramp-show-ad-hoc-proxies.

* lisp/net/tramp.el (tramp-show-ad-hoc-proxies): New defcustom.
(tramp-make-tramp-file-name): Use it.
(tramp-make-tramp-hop-name): Don't add hop twice.

* test/lisp/net/tramp-tests.el (tramp-test02-file-name-dissect)
(tramp-test02-file-name-dissect-simplified)
(tramp-test02-file-name-dissect-separate): Adapt tests.

doc/misc/tramp.texi

@@ -3644,10 +3644,20 @@ Each involved method must be an inline method (@pxref{Inline methods}).
 @code{tramp-default-proxies-alist} and is available for re-use during
 that Emacs session.  Subsequent @value{tramp} connections to the same
 remote host can then use the shortcut form:
-@samp{@trampfn{ssh,you@@remotehost,/path}}.  Ad-hoc definitions are
-removed from @code{tramp-default-proxies-alist} via the command
-@kbd{M-x tramp-cleanup-all-connections @key{RET}} (@pxref{Cleanup
-remote connections}).
+@samp{@trampfn{ssh,you@@remotehost,/path}}.
+
+@defopt tramp-show-ad-hoc-proxies
+If this user option is non-@code{nil}, ad-hoc definitions are kept in
+remote file names instead of showing the shortcuts.
+
+@lisp
+(customize-set-variable 'tramp-show-ad-hoc-proxies t)
+@end lisp
+@end defopt
+
+Ad-hoc definitions are removed from @code{tramp-default-proxies-alist}
+via the command @kbd{M-x tramp-cleanup-all-connections @key{RET}}
+(@pxref{Cleanup remote connections}).
 
 @defopt tramp-save-ad-hoc-proxies
 For ad-hoc definitions to be saved automatically in

lisp/net/tramp.el

@@ -520,6 +520,11 @@ interpreted as a regular expression which always matches."
   :version "24.3"
   :type 'boolean)
 
+(defcustom tramp-show-ad-hoc-proxies nil
+  "Whether to show ad-hoc proxies in file names."
+  :version "29.2"
+  :type 'boolean)
+
 ;; For some obscure technical reasons, `system-name' on w32 returns
 ;; either lower case or upper case letters.  See
 ;; <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=38079#20>.
@@ -1802,8 +1807,8 @@ the form (METHOD USER DOMAIN HOST PORT LOCALNAME &optional HOP)."
       (when (cadr args)
 	(setq localname (and (stringp (cadr args)) (cadr args))))
       (when hop
-	;; Keep hop in file name for completion.
-	(unless minibuffer-completing-file-name
+	;; Keep hop in file name for completion or when indicated.
+	(unless (or minibuffer-completing-file-name tramp-show-ad-hoc-proxies)
 	  (setq hop nil))
 	;; Assure that the hops are in `tramp-default-proxies-alist'.
 	;; In tramp-archive.el, the slot `hop' is used for the archive
@@ -1853,7 +1858,7 @@ the form (METHOD USER DOMAIN HOST PORT LOCALNAME &optional HOP)."
     (replace-regexp-in-string
      (rx (regexp tramp-postfix-host-regexp) eos)
      tramp-postfix-hop-format
-     (tramp-make-tramp-file-name vec 'noloc)))))
+     (tramp-make-tramp-file-name (tramp-file-name-unify vec))))))
 
 (defun tramp-completion-make-tramp-file-name (method user host localname)
   "Construct a Tramp file name from METHOD, USER, HOST and LOCALNAME.