minibuffer-complete
minibuffer-complete is an interactive compiled Lisp function in `minibuffer.el
'.
(minibuffer-complete)
Complete the minibuffer contents as far as possible.
Return nil if there is no valid completion, else t.
If no characters can be completed, display a list of possible completions.
If you repeat this command after it displayed such a list,
scroll the window of possible completions.