Here is a realisation from my recent work: it is not if the data is relational - because if you need you can always push the data into relations - just like you can push it into hierarchies if all you have is files and directories. It is about how much churn there is in the relations. You can model relations with just links or something and if there is not much churn you can keep it in git and it will work OK - the problem starts when your relations start churning (like when you have reviews that need to be updated on both review instruction change and document change) this is when you see yourself start building a relational db (badly).