++++
+*** A New option 'dired-always-read-filesystem' default to nil.
+If non-nil, buffers visiting files are reverted before search them;
+for instance, in 'dired-mark-files-containing-regexp' a non-nil value
+of this option means the file is revisited in a temporary buffer;
+this temporary buffer is the actual buffer searched: the original buffer
+visiting the file is not modified.
+