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

It looks like if the readonly attribute is set, then msbuild sets the Normal, it does not just clear ReadOnly. I created a file and marked it with Hidden only and ran msbuild to copy the file and Hidden was maintained. When I also marked it as ReadOnly, once copied Hidden AND ReadOnly were cleared. So, I think the way it is currently implemented matches what msbuild does.