ignoring subdirectory in find-file completion

[Albert Reiner]

Hi,

I am looking for some way to make completion when using find-file
ignore any directory named _darcs; i.e., if I have a directory
structure

    foo/
      _darcs/
        ...
      bar/
        ...

then `M-x find-file f o o / TAB' should complete to `foo/bar/'.

>From the documentation I thought that

    (add-to-list 'completion-ignored-extensions "_darcs")

should do what I want, but that does not seem to be the case.

Any help would be appreciated.

Albert.