`fill` is dangerous :-(

I propose to add an extra keyword argument to fill (and fill!) to specify copy instead of reference and switch to copy in Julia 2.0 :slight_smile:

While it makes sense to have call by sharing in functions, there is not much intuitions (at least for me) behind referencing the same object in fill… after all we are not modifying it, we “copy” it in different positions of the filled array…