Function merge_option 

pub fn merge_option<T>(
    to: &mut Option<T>,
    from: Option<T>,
    merge_fn: impl FnOnce(&mut T, T) -> DidMerge,
) -> DidMerge

A utility for implementing Analysis::merge when the Data type is an Option.

Always take a Some over a None and calls the given function to merge two Somes.