`Highlight completion' is a variant on completion in Emacs. Normally if you're typing a file name into the minibuffer in Emacs, when you hit the TAB key, Emacs completes what you already have as far as possible. This package augments this by displaying the text that Emacs would add if you hit the TAB key, highlighted. (The idea is that, if you're not looking at the screen, you won't know that anyt