we only need something like the trac-svn-hook script.
This is the only thing that's arguably missing here. But I don't really know enough about shell scripting, Git hooks and the Git data model to do this.
So I'm simply closing this ticket without that (non-essential?) script. If someone wants to contribute a script in the next few days please reopen. (After the 1.0 release a new ticket should be created.)