-Compare the current file (the file at point) with another file (the
-file at the mark) using the @code{diff} program (@code{dired-diff}).
-The file at the mark is the first argument of @code{diff}, and the
-file at point is the second argument. This refers to the ordinary
-Emacs mark, not Dired marks; use @kbd{C-@key{SPC}}
-(@code{set-mark-command}) to set the mark at the first file's line
-(@pxref{Setting Mark}).
-
-@findex dired-backup-diff
-@kindex M-= @r{(Dired)}
-@item M-=
-Compare the current file with its latest backup file
-(@code{dired-backup-diff}). If the current file is itself a backup,
-compare it with the file it is a backup of; this way, you can compare
-a file with any one of its backups.
-
-The backup file is the first file given to @code{diff}.
-@end table
+ The @kbd{=} (@code{dired-diff}) command compares the current file
+(the file at point) with another file (read using the minibuffer)
+using the @command{diff} program. The file specified with the
+minibuffer is the first argument of @command{diff}, and file at point
+is the second argument. The output of the @command{diff} program is
+shown in a buffer using Diff mode (@pxref{Comparing Files}).
+
+ If the region is active, the default for the file read using the
+minibuffer is the file at the mark (i.e., the ordinary Emacs mark,
+not a Dired mark; @pxref{Setting Mark}). Otherwise, if the file at
+point has a backup file (@pxref{Backup}), that is the default.