Problem scenario
You are not sure if environmental specific values should be placed into version control. What should do you?
Solution
Some people think that everything should go into version control. But others disagree. Here are examples of each philosophy:
"You need to get everything in version control. Everything. Not just the code, but everything required to build the environment." (This was taken from page 297 of The Phoenix Project.) This is very clear in how it disagrees with the twelve-factor app principles.
"The twelve-factor app stores config in environment variables (often shortened to env vars or env). Env vars are easy to change between deploys without changing any code; unlike config files, there is little chance of them being checked into the code repo accidentally;" (This quote was taken from https://12factor.net/config.)