Prevent? Not sure you can in any reasonable fashion. The only way I've seen places seriously curb exfiltration of code was by forcing everyone to use thin clie

Prevent? Not sure you can in any reasonable fashion. The only way I've seen places seriously curb exfiltration of code was by forcing everyone to use thin clients to remote into locked-down windows desktops hosted on cloud infrastructure. These remote images could access the source. Your only other options are NDAs and trusting your people. And if you can show someone leaked something, for definite, try the court system.