What: GIT - Tree History Storage Tool
Where: http://www.gitscm.org/ http://git.or.cz/ http://ozlabs.org/~paulus/gitk/ Description: Currently at version 2.6.12 . Updated: 01/2006 Contact: See web site
It is related to Tcl/Tk because there is gitk, a history visualization tool written in Tcl/Tk.