* ivy.el (ivy-minibuffer-map): Bind "C-j" to visit a directory without
exiting the minibuffer.
(ivy--directory): New defvar.
(ivy-done): Expand file names.
(ivy-alt-done): New defun.
(ivy-backward-delete-char): When completing file names, visit the parent dir.
(ivy-read): Add the predicate argument, similar to `completing-read'.
All code that uses `ivy-read' needs to be updated. Move the collection/predicate stuff here.
(ivy-completing-read): Update.
(ivy--insert-prompt): Display the current directory when completing file names.