What are the best practices for versioning and testing prompts in production?

I'm working on a production system where we use GPT-4 for various tasks. As we iterate on our prompts, I'm concerned about:

1. Version control: How do you track prompt changes over time?
2. A/B testing: What's the best way to test prompt variations?
3. Regression testing: How do you ensure new prompts don't break existing functionality?
4. Monitoring: What metrics should we track for prompt performance?

We currently just have prompts in our codebase, but I feel like we need a more robust system. What tools and processes do successful AI teams use for prompt management?