Choice of SCM for the Tcl/Tk core

As of 2015-04-04, the SCM for the Tcl/Tk core (and many related packages) is Fossil.

At some previous point in time, it was under the control of CVS hosted on SourceForge. The reasons behind the move and the choice of Fossil and self-hosting are probably lost in the sands of time (or chat logs and mailing list histories).