[[!comment format=mdwn username="spwhitton" subject="comment 8" date="2015-12-02T21:44:37Z" content=""" My original goal was to have `Apt.buildDep` return NoChange if the build deps are already installed. As a welcome but unexplained side-effect, on my system `noChangeIfUnchanged` *does* cause apt's output not to be displayed. I'll think about ways to combine our two combinators. """]]