Gitit is a wiki is a form of software that uses a distributed revision control system, like Git that is used to manage the wikis history.
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Pro Lots of export formats
Giti has a multitude of formats that it allows to be exported, including LaTeX, ConTeXt, DocBook, RTF, OpenOffice ODT, and MediaWiki markup.
Pro Supports markdown
Getit supports markdown, a plain text formatting syntax that is designed so that it can be read by HTML.
Pro Free and open source software (FOSS)
Licensed under GPLv2 so you can download source code and customize to meet your needs, provided that you know or are willing to learn Haskell.
Pro Can be used collaboratively by multiple people
Pro Renders math
Con Requires Haskell
On some Linux platforms a binary package for Haskell may not be included in the standard repositories. So, it will be necessary to compile Haskell from source code or find a non-standard package repository, which may seem like a hassle if you don't use Haskell for anything else.