Function write_size_diff 

pub fn write_size_diff(
    writer: &mut impl Write,
    size_old: Size,
    size_new: Size,
) -> Result

Writes a formatted size difference between two sizes to the provided writer.

This function displays both the absolute sizes (old → new) and the difference between them, with appropriate coloring (red for size increase, green for size decrease).

Returns

Returns Ok(()) when successful.

Errors

Returns Err when writing to writer fails.