Fix inconsistency expanding "//" in Tramp

* doc/misc/tramp.texi (File name completion): Adapt example
expanding "//".

* lisp/net/tramp.el (tramp-handle-substitute-in-file-name): "//" shall
expand the localname only, even when on top of the local part.

* test/lisp/net/tramp-tests.el (tramp-test04-substitute-in-file-name):
Adapt test.

1 files changed, 11 insertions, 9 deletions

diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 09abd482260..b2e20000d3f 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -3554,17 +3554,19 @@ support symbolic links."
     ;; First, we must replace environment variables.
     (setq filename (tramp-replace-environment-variables filename))
     (with-parsed-tramp-file-name filename nil
-      ;; Ignore in LOCALNAME everything before "//" or "/~".
-      (when (and (stringp localname) (string-match ".+?/\\(/\\|~\\)" localname))
-        (setq filename
-              (concat (file-remote-p filename)
-                      (replace-match "\\1" nil nil localname)))
-        ;; "/m:h:~" does not work for completion.  We use "/m:h:~/".
-        (when (string-match "~$" filename)
-          (setq filename (concat filename "/"))))
       ;; We do not want to replace environment variables, again.
       (let (process-environment)
-        (tramp-run-real-handler 'substitute-in-file-name (list filename))))))
+        ;; Ignore in LOCALNAME everything before "//" or "/~".
+        (when (stringp localname)
+          (if (string-match "//\\(/\\|~\\)" localname)
+              (setq filename (substitute-in-file-name localname))
+            (setq filename
+                  (concat (file-remote-p filename)
+                          (substitute-in-file-name localname))))))
+      ;; "/m:h:~" does not work for completion.  We use "/m:h:~/".
+      (if (string-match "~$" filename)
+          (concat filename "/")
+        filename))))
 
 (defun tramp-handle-set-visited-file-modtime (&optional time-list)
   "Like `set-visited-file-modtime' for Tramp files."