[aljarry]

Github Actions Runner code is pretty easy to read, here's a specific place that define default arguments for popular shells / binaries: https://github.com/actions/runner/blob/main/src/Runner.Worke..., it is exported through a method ScriptHandlerHelpers.GetScriptArgumentsFormat.

In ScriptHandler.cs there's all the code for preparing process environment, arguments, etc. but specifically here's actual code to start the process:

https://github.com/actions/runner/blob/main/src/Runner.Worke...

Overall I was positively surprised at simplicity of this code. It's very procedural, it handles a ton of edge cases, but it seems to be easy to understand and debug.