+ If an element of the list in @code{completion-ignored-extensions} ends
+in a slash @file{/}, it indicates a subdirectory that should be ignored
+when completing file names. (Elements of
+@code{completion-ignored-extensions} which do not end in a slash are
+never considered when a completion candidate is a directory; thus,
+completion returns directories whose names end in @file{.elc} even
+though there's an element @code{".elc"} in the list.)
+