Consider TRAC. It free/open source integrated wiki for documentation, bug tracker, subversion/Git/mercurial/... code repository, and code viewer. Code viewer is smart enough to parse comments in code and correctly interpret them as hyperlinks to docs or bug tracker. Comments in bug tracker can expands to changeset, etc.
Atlassian wiki (confluence) is very unlike other wiki (adding styles formatting to plain text (markdown), so text is more complex to reuse (or use by outside tools). Usually you get better and more flexible tools from open source community.