Some minor Tramp fixes, resulting from test campaign

* lisp/net/tramp.el (tramp-handle-write-region):
* lisp/net/tramp-adb.el (tramp-adb-handle-write-region):
* lisp/net/tramp-sh.el (tramp-sh-handle-write-region):
* lisp/net/tramp-smb.el (tramp-smb-handle-write-region): Use `current-time'
if needed.

* lisp/net/tramp-gvfs.el (tramp-gvfs-gio-mapping):
(tramp-gvfs-do-copy-or-rename-file): Remove "gvfs-rename", it is
not trustworthy.

* test/lisp/net/tramp-tests.el (tramp-test07-file-exists-p): Check also for
symlinked files in trash.
(tramp-test20-file-modes): Revert last change, it was a thinko.

lisp/net/tramp-adb.el

@@ -575,8 +575,9 @@ But handle the case, if the \"test\" command is not available."
       ;; Set file modification time.
       (when (or (eq visit t) (stringp visit))
 	(set-visited-file-modtime
-	 (tramp-compat-file-attribute-modification-time
-	  (file-attributes filename))))
+	 (or (tramp-compat-file-attribute-modification-time
+	      (file-attributes filename))
+	     (current-time))))
 
       ;; The end.
       (when (and (null noninteractive)

lisp/net/tramp-gvfs.el

@@ -689,7 +689,6 @@ It has been changed in GVFS 1.14.")
     ("gvfs-monitor-file" . "monitor")
     ("gvfs-mount" . "mount")
     ("gvfs-move" . "move")
-    ("gvfs-rename" . "rename")
     ("gvfs-rm" . "remove")
     ("gvfs-set-attribute" . "set"))
   "List of cons cells, mapping \"gvfs-<command>\" to \"gio <command>\".")
@@ -985,15 +984,12 @@ file names."
 	(copy-directory filename newname keep-date t)
 	(when (eq op 'rename) (delete-directory filename 'recursive)))
 
-    (let* ((t1 (tramp-tramp-file-p filename))
-	   (t2 (tramp-tramp-file-p newname))
-	   (equal-remote (tramp-equal-remote filename newname))
-	   (gvfs-operation
-	    (cond
-	     ((eq op 'copy) "gvfs-copy")
-	     (equal-remote "gvfs-rename")
-	     (t "gvfs-move")))
-	   (msg-operation (if (eq op 'copy) "Copying" "Renaming")))
+    (let ((t1 (tramp-tramp-file-p filename))
+	  (t2 (tramp-tramp-file-p newname))
+	  (equal-remote (tramp-equal-remote filename newname))
+	  ;; "gvfs-rename" is not trustworthy.
+	  (gvfs-operation (if (eq op 'copy) "gvfs-copy" "gvfs-move"))
+	  (msg-operation (if (eq op 'copy) "Copying" "Renaming")))
 
       (with-parsed-tramp-file-name (if t1 filename newname) nil
 	(unless (file-exists-p filename)
@@ -2439,7 +2435,10 @@ This uses \"avahi-browse\" in case D-Bus is not enabled in Avahi."
 
 (when tramp-gvfs-enabled
   ;; Suppress D-Bus error messages and Tramp traces.
-  (let ((tramp-verbose 0)
+  (let (;; Sometimes, it fails with "Variable binding depth exceeds
+	;; max-specpdl-size".  Shall be fixed in Emacs 27.
+	(max-specpdl-size (* 2 max-specpdl-size))
+	(tramp-verbose 0)
 	tramp-gvfs-dbus-event-vector fun)
     ;; Add completion functions for services announced by DNS-SD.
     ;; See <http://www.dns-sd.org/ServiceTypes.html> for valid service types.

lisp/net/tramp-sh.el

@@ -3530,7 +3530,8 @@ implementation will be used."
              ;; We must pass modtime explicitly, because FILENAME can
              ;; be different from (buffer-file-name), f.e. if
              ;; `file-precious-flag' is set.
-             (tramp-compat-file-attribute-modification-time file-attr))
+	     (or (tramp-compat-file-attribute-modification-time file-attr)
+		 (current-time)))
             (when (and (= (tramp-compat-file-attribute-user-id file-attr) uid)
                        (= (tramp-compat-file-attribute-group-id file-attr) gid))
               (setq need-chown nil))))

lisp/net/tramp-smb.el

@@ -1630,8 +1630,9 @@ errors for shares like \"C$/\", which are common in Microsoft Windows."
       ;; Set file modification time.
       (when (or (eq visit t) (stringp visit))
 	(set-visited-file-modtime
-	 (tramp-compat-file-attribute-modification-time
-	  (file-attributes filename))))
+	 (or (tramp-compat-file-attribute-modification-time
+	      (file-attributes filename))
+	     (current-time))))
 
       ;; The end.
       (when (and (null noninteractive)

lisp/net/tramp.el

@@ -4181,8 +4181,9 @@ of."
       ;; Set file modification time.
       (when (or (eq visit t) (stringp visit))
 	(set-visited-file-modtime
-	 (tramp-compat-file-attribute-modification-time
-	  (file-attributes filename))))
+	 (or (tramp-compat-file-attribute-modification-time
+	      (file-attributes filename))
+	     (current-time))))
 
       ;; Set the ownership.
       (tramp-set-file-uid-gid filename uid gid))

test/lisp/net/tramp-tests.el

@@ -2281,9 +2281,13 @@ This checks also `file-name-as-directory', `file-name-directory',
 	  (delete-file tmp-name 'trash)
 	  (should-not (file-exists-p tmp-name))
 	  (should
-	   (file-exists-p
-	    (expand-file-name
-	     (file-name-nondirectory tmp-name) trash-directory)))
+	   (or (file-exists-p
+		(expand-file-name
+		 (file-name-nondirectory tmp-name) trash-directory))
+	       ;; Gdrive.
+	       (file-symlink-p
+		(expand-file-name
+		 (file-name-nondirectory tmp-name) trash-directory))))
 	  (delete-directory trash-directory 'recursive)
 	  (should-not (file-exists-p trash-directory)))))))
 
@@ -3473,7 +3477,10 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
   (skip-unless
    (or (tramp--test-sh-p) (tramp--test-sudoedit-p)
        ;; Not all tramp-gvfs.el methods support changing the file mode.
-       (tramp--test-gvfs-p "afp") (tramp--test-gvfs-p "ftp")))
+       (and
+	(tramp--test-gvfs-p)
+	(string-match-p
+	 "ftp" (file-remote-p tramp-test-temporary-file-directory 'method)))))
 
   (dolist (quoted (if (tramp--test-expensive-test) '(nil t) '(nil)))
     (let ((tmp-name1 (tramp--test-make-temp-name nil quoted))