bug#41412: 27.0.90; Value of default directory in completions buffer

[Stefan Monnier]

> Aha.  But then what would the correct fix now?  I haven't tried the
> proposed change (i.e., just change to `file-name-directory'), but it
> sounds logical to me.  That is, if the user has typed "~/foo/bar/zo"
> then use "~/foo/bar" as the default directory.

I think the correct thing to do is to look at the `(cdr (last completions))`
where `completions` is what `completion-all-completions` returned.
That gives what used to be called `completion-base-size`.


        Stefan