ediff-patch-file

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

It is bound to <menu-bar> <tools> <epatch> <ediff-patch-file>.

(ediff-patch-file &optional ARG PATCH-BUF)

Query for a file name, and then run Ediff by patching that file.
If optional PATCH-BUF is given, use the patch in that buffer
and don't ask the user.
If prefix argument, then: if even argument, assume that the patch is in a
buffer. If odd -- assume it is in a file.