Ask HN: What is the best tool/service to keep credentials out of GitHub?

I recently started working with a new client. They are a fast growing startup with a successful product. They had previously outsourced some of their initial development. They had only one computer programmer on staff, and he is very junior, with just 1 year of experience. I've been called in to help them hire a tech team and put in places various best practices. One mistake that had previously been made was credentials for 3rd party APIs were embedded in the code and uploaded to Github. Not too big a deal, no harm done, nothing leaked to the public, but still, I'd like to put in place some automatic monitoring to protect us from this. I'm aware of 3rd party services such as https://cybelangel.com/ but in the past I had the odd experience of getting a warning several weeks after a breach. It would be better to have a much faster warning. Please assume code that contains NodeJS and JVM code. Please assume a fairly traditional devops setup, which might rely on something like Jenkins for deployment. I'd be grateful for any suggestions regarding: 1. 3rd party security monitoring services that you've had a good experience with 2. or tools specific for NodeJS 3. or tools specific for JVM code 4. or tools specific to Github Anything that has worked for you, for catching things like usernames/passwords, please let me know.