bug#5496: xdev rename-file of symlinks-to-directories broken

[David De La Harpe Golden]

So, file-directory-p returns non-nil for symlinks to directories, so 
delete-directory now (i.e. following #5436/#3353) gets incorrectly 
called in rename-file if you try to rename a symlink-to-a-directory to a 
location on another device.  The copy-directory bit is already guarded 
appropriately, but not the delete-directory bit.

delete-directory at least then fails rather than following the symlink 
and then recursively deleting. However, the result a user would no doubt 
expect is for just the symlink to be renamed.

e.g. /tmp and /home different filesystems

mkdir /home/david/foo
cd /tmp
mkdir bar
ln -s bar baz

; in emacs
(rename-file "/tmp/baz" "/home/david/foo")

result:
baz symlink to a "bar" in /home/david/foo
- consistent with shell mv behaviour.
Unfortunately, /tmp/baz won't be removed properly without attached tiny 
patch.


=== modified file 'src/fileio.c'
--- src/fileio.c        2010-01-28 17:47:05 +0000
+++ src/fileio.c        2010-01-30 01:50:33 +0000
@@ -2295,17 +2295,21 @@
            /* We have already prompted if it was an integer, so don't
               have copy-file prompt again.  */
            Fcopy_file (file, newname,
                        NILP (ok_if_already_exists) ? Qnil : Qt,
                        Qt, Qt);
 
          count = SPECPDL_INDEX ();
          specbind (Qdelete_by_moving_to_trash, Qnil);
-         if (!NILP (Ffile_directory_p (file)))
+         if (
+#ifdef S_IFLNK
+              (NILP (symlink_target)) &&
+#endif
+              (!NILP (Ffile_directory_p (file))))
            call2 (Qdelete_directory, file, Qt);
          else
            Fdelete_file (file);
          unbind_to (count, Qnil);
        }
       else
        report_file_error ("Renaming", list2 (file, newname));
     }