As little as possible. I think there's an extent to which the trend for 'memory hacking' is a little harmful. The field of modern software is too broad to possibly remember much of it so it's better to learn how to find answers well and quickly than memorise things. I know about 4 common git commands by memory and everything else I know how to Google (DDG) the answer. Using a language with a good IDE also helps, your tools should assist you to build working things rather than tangling with parameter order trivia.