slide/mono — comment on commit 407dd029e3f1ec712a7f6a8b684b8ee8d2a18b61
File: mcs/class/Microsoft.Build.Tasks/Microsoft.Build.Tasks/Copy.cs line 213
By slide:

That is a possibility. I am not sure how msbuild does it, I will try setting the Hidden attribute on a file to be copied and see what attributes the resulting file has (if it maintains the Hidden attribute).