discourse/discourse — pull request #1062 by ComputerDruid (2013-06-21 01:48:10+00:00)
Title: Use "command -v" to test for convert instead of "which -s"

Command -v is generally considered to be more portable, see also the discussion here: http://meta.discourse.org/t/admin-warns-imagemagick-not-installed-when-it-is/7673/4