<!-- Microsoft.* packages will only come from nuget.org. -->
<!-- All other packages come from contoso.com by default. -->
<packageSourceMapping>
  <packageSource key="nuget.org">
    <package pattern="Microsoft.*" />
  </packageSource>
  <packageSource key="contoso.com">
    <package pattern="*" />
  </packageSource>
</packageSoureMapping>