Function garden::eval::tree_value_for_shell

pub fn tree_value_for_shell(
    app_context: &ApplicationContext,
    config: &Configuration,
    expr: &str,
    tree_name: &TreeName,
    garden_name: Option<&GardenName>
) -> String

Resolve an expression in a garden/tree/global scope for execution by a shell. This is used to generate the commands used internally by garden.