LogSubstPol is a TFS check-in policy which insertes the check-in comments and other keywords into your source code, so you can keep track of the changes even if you are not connected to TFS.
It can be compared with the $log$ (and other) substitition in any other CVS systems.
This release has full support for other keywords like: $Author$, $Source$, $Date$, $Id$, $Header$, $RCSFile$, $PrevRevision$, $Revision$