Prewiking: when gollum displays page, it render it by wiki syntax of your choice (creole, textile, markdown, etc).
But before it, gollum expands links in form [[link]]. and one form of gollumwiki is [[Text to display|http://exapmlec.om]], which is exactly oposite as in creole (and as natural). See https://github.com/github/gollum#page-links