I heard about Gerrit at the recent PTP meeteing.
https://code.google.com/p/gerrit/
Gerrit manages the process of code reviewing in git, and has a lot of customization. You can set things up so that no one can push to the main branch unless their change has been reviewed. You can make rules like, one senior developer and two junior developers must review, etc. By helping to enforce code reviews, Gerrit helps to increase code quality, and helps to train junior developers in understanding the codebase. I think it might be a good alternative to Trac.
Cheers, Steve