slide/mono — comment on commit 407dd029e3f1ec712a7f6a8b684b8ee8d2a18b61
File: mcs/class/Microsoft.Build.Tasks/Microsoft.Build.Tasks/Copy.cs line 207
By radical:

One last check. The unconditional clearing of attributes, does that happen in non-4.0 projects also?
Run msbuild with /tv:2.0 to check.