For GSoC, we should really insist that the coders try to get their code
on trac from the start. In particular, they should follow the "one
ticket, one issue" rule and not just dump everything on one ticket.
I have seen some GSoC projects where one person codes for the summer,
puts the code on Trac and then disappears. The code will never get
merged because it has issues or because it is simply too big to be
reviewed in a reasonable way.
As an example of how to do this right, I recommend:
http://trac.sagemath.org/ticket/17601
Jeroen.