Recent stat from coreutils could break Tramp

[Michael Albinus]

Hi,

I've just installed the appended patch to the master branch as
6aad36ace9953b9672b13be68416d205532d5e59. The problem is, that the stat
program has changed its output format; it will break Tramp for some
special characters in file names. It's a pity that this has been shown
such late; it came to me after upgrading my development machine to
Ubuntu 16.04.

I've reported the problem to the coreutils maintainers as bug#23422, and
they promised to fix it. However, the current tramp-tests.el reports a
failed test.

The fix is very simple. Shall I backport (cherrypick) it also to the
emacs-25 branch?

Best regards, Michael.

*** 
/usr/local/src/emacs/lisp/net/tramp-sh.el.~6e790b71efae6003b9fa701a8630ee69e0a94294~
        2016-05-05 10:40:11.455293200 +0200
--- /usr/local/src/emacs/lisp/net/tramp-sh.el   2016-05-05 10:19:50.567195614 
+0200
***************
*** 5430,5442 ****
                   vec "stat" (tramp-get-remote-path vec)))
          tmp)
        ;; Check whether stat(1) returns usable syntax.  "%s" does not
!       ;; work on older AIX systems.
        (when result
        (setq tmp
              (tramp-send-command-and-read
               vec (format "%s -c '(\"%%N\" %%s)' /" result) 'noerror))
        (unless (and (listp tmp) (stringp (car tmp))
!                    (string-match "^./.$" (car tmp))
                     (integerp (cadr tmp)))
          (setq result nil)))
        result)))
--- 5430,5444 ----
                   vec "stat" (tramp-get-remote-path vec)))
          tmp)
        ;; Check whether stat(1) returns usable syntax.  "%s" does not
!       ;; work on older AIX systems.  Recent GNU stat versions (8.24?)
!       ;; use shell quoted format for "%N", we check the boundaries "`"
!       ;; and "'", therefore.  See Bug#23422 in coreutils.
        (when result
        (setq tmp
              (tramp-send-command-and-read
               vec (format "%s -c '(\"%%N\" %%s)' /" result) 'noerror))
        (unless (and (listp tmp) (stringp (car tmp))
!                    (string-match "^`/'$" (car tmp))
                     (integerp (cadr tmp)))
          (setq result nil)))
        result)))