Change default behavior of completion-ignored-extensions

[Andrew Korty]

Greetings.  How can I change the way completion-ignored-extensions is
used by find-file?

As it is, "lists of possible completions" aren't affected by this
variable:

,----[ C-h v completion-ignored-extensions RET ]
| Documentation:
| *Completion ignores filenames ending in any string in this list.
| This variable does not affect lists of possible completions,
| but does affect the commands that actually do completions.
`----

I'd like to add ./ and ../ to this variable and be able to
tab-complete right through a directory with only one interesting
entry.  For example, if I have a directory ~/foo/ containing a
subdirectory bar/, I should be able to type

        M-x find-file RET ~/foo TAB

and end up with ~/foo/bar/ in the minibuffer instead of first getting
"[Complete, but not unique]", hitting TAB again, getting
"Completion List" buffer containing ./, ../, and bar/, and having to
type "b TAB" to finally get what should have been obvious.

I understand that completion-ignored-extensions is not supposed to
work this way, but I want to change that behavior.  It seems like I
should be able to advise minibuffer-complete, but I haven't figured
out how to do that successfully.

-- 
Andrew J. Korty, Principal Security Engineer, GCIA, GCFA
Office of the Vice President for Information Technology
Indiana University