Q on read-file-name and completion-ignored-extensions

[Drew Adams]

Function `read-file-name' does not seem to respect
`completion-ignored-extensions'. This is true in Emacs 22 and as far back as
Emacs 20. Some questions:

1. Is this on purpose or an old bug?

2. If on purpose, then shouldn't the doc string of
`completion-ignored-extensions' be changed slightly? It says:

 This variable does not affect lists of possible completions,
 but does affect the commands that actually do completions.

(BTW, "do completion" or "complete input" would be better than "do
completions", here.)

The case of `read-file-name' itself is neither - it does not produce a list
of completions and it is not a command that completes input.

But when you hit TAB at the prompt from `read-file-name', shouldn't
`minibuffer-complete' respect that variable, according to its doc string?
(TAB is bound to `minibuffer-complete', a "command that does completion".)

If the current behavior is by design, then perhaps the doc string should say
something about this case. I'm not sure what it should say, because I don't
know if `read-file-name' is the only exception to letting "commands that
actually do completion" respect the variable.