ediff-directories3

ediff-directories3 is an interactive autoloaded compiled Lisp function in `ediff.el'.

It is bound to <menu-bar> <tools> <compare> <ediff-directories3>.

(ediff-directories3 DIR1 DIR2 DIR3 REGEXP)

Run Ediff on three directories, DIR1, DIR2, and DIR3, comparing files that
have the same name in all three. The last argument, REGEXP, is nil or a
regular expression; only file names that match the regexp are considered.