Requires better docstring: icomplete-completions function

[Jean Louis <bugs@gnu.support>]

This function is not well defined, I would like to use some built-in
Emacs completion that could replace packages that are not
built-in. But this function description does not tell me how
candidates structure looks like or what should be predicate.


icomplete-completions is a compiled Lisp function in ‘icomplete.el’.

(icomplete-completions NAME CANDIDATES PREDICATE REQUIRE-MATCH)

Identify prospective candidates for minibuffer completion.

The display is updated with each minibuffer keystroke during
minibuffer completion.

Prospective completion suffixes (if any) are displayed, bracketed by
one of (), [], or {} pairs.  The choice of brackets is as follows:

  (...) - a single prospect is identified and matching is enforced,
  [...] - a single prospect is identified but matching is optional, or
  {...} - multiple prospects, separated by commas, are indicated, and
          further input is required to distinguish a single one.

If there are multiple possibilities, ‘icomplete-separator’ separates them.

The displays for unambiguous matches have ‘ [Matched]’ appended
(whether complete or not), or ‘ [No matches]’, if no eligible
matches exist.