copies: split the combination of the copies mapping in its own function...
copies: split the combination of the copies mapping in its own function
In some case, this part take up to 95% of the copy tracing that take about a
hundred second. This poor performance comes from the fact we keep duplciating
and merging dictionary that are mostly similar.
I want to experiment with smarter native code to do this, so I need to isolate
the function first.