We have recently upgraded from TFS 2012 to 2013. One of the new features in Visual Studio 2013 is the CodeLens or Code Indicators which can pull associated work item, changeset and test impact data from TFS for many members in code (classes, properties, methods, etc).
It is my understanding that it gets these references through and indexing task on the server. Having upgraded, I had wanted to see previous work reflected in the indicators, but alas all I had where the reference indicators.