An alternative used by another team at Adobe that I just left is to use what we called a "mutex," which is basically an e-mail negotiation for exclusive write access to the sourcebase. In other words, when I have set of changes I want to contribute, I send e-mail requesting the mutex. I then check in my changes, pull them down on the other platform, verify them, make fixes as needed, and send another e-mail releasing the mutex. During the time I hold the mutex, it is understood that no other team member may check in and anyone who syncs to the database runs the risk of getting unfinished code.