+(defcustom dired-always-read-filesystem nil
+ "Non-nil means revert buffers visiting files before searching them.
+ By default, commands like `dired-mark-files-containing-regexp' will
+ search any buffers visiting the marked files without reverting them,
+ even if they were changed on disk. When this option is non-nil, such
+ buffers are always reverted in a temporary buffer before searching
+ them: the search is performed on the temporary buffer, the original
+ buffer visiting the file is not modified."
+ :type 'boolean
+ :version "25.2"
+ :group 'dired)
+