bug#19031: 24.4; find-file in icomplete-mode shows completions with no input

[Eli Zaretskii]

> From: Andrii Kolomoiets <andreyk.mad@gmail.com>
> Date: Tue, 08 Dec 2020 12:43:21 +0200
> Cc: Ole Laursen <olau@iola.dk>, Lars Ingebrigtsen <larsi@gnus.org>,
>  19031@debbugs.gnu.org
> 
> 1. emacs -Q
> 2. M-: (setq insert-default-directory nil)
> 3. M-x icomplete-mode
> 4. C-x C-f ~/
> 
> In this case everything works as described by the docstring: user input
> is here so completions are shown.  But IMO Ole's issue is not
> completely solved: bunch of uninteresting dotfiles are shown.

Emacs never filters out the dotfiles, not by default anyway.  Try
"C-x C-f TAB TAB", and you will see that.  IMO, it would be confusing
if some completion packages did this and some didn't.

> If the 'read-file-name-default' function can set the
> 'minibuffer-default' variable to the substring of the minibuffer content
> from (minibuffer-prompt-end) to the last occurence of the path
> separator, then, in addition to the patched 'icomplete-exhibit', this
> can give desired result: no completions will be show until some input
> after path separator.

But file-name input is not limited to absolute file names.  The user
can legitimately enter a relative file name, in which case the
separator may not be present at all.