Targets to discover and set README and PackageIcon based on Item metadata

Directory.Build.targets

  <!--
    If no PackageReadmeFile is present and there's a _PackageFiles with the metadata node `PackageReadmeFile="true"` set,
    use its resolved PackagePath as the `PackageReadmeFile`

    eg. <None Include="../../README.md" Pack="true" PackagePath="\" PackageReadmeFile="true" />
   -->
  <Target Name="_SetPackageReadmeFileByConvention"
          DependsOnTargets="_GetPackageFiles"
          BeforeTargets="GenerateNuspec"
          Condition="'$(PackageReadmeFile)' == ''">
    <ItemGroup>
      <DiscoveredReadmeFile Include="@(_PackageFiles)" Condition="'%(_PackageFiles.PackageReadmeFile)' == 'true'">
        <_PackagePath>%(_PackageFiles.PackagePath)</_PackagePath>
        <_PackagePath Condition="'%(_PackageFiles.PackagePath)' == '/'"></_PackagePath>
      </DiscoveredReadmeFile>
    </ItemGroup>
    <PropertyGroup Condition="'@(DiscoveredReadmeFile)' != ''">
      <PackageReadmeFile>%(DiscoveredReadmeFile._PackagePath)$([System.IO.Path]::GetFileName(%(DiscoveredReadmeFile.Identity)))</PackageReadmeFile>
    </PropertyGroup>
  </Target>
    <!--
    If no PackageIcon is present and there's a _PackageFiles with the metadata node `PackageIcon="true"` set,
    use its resolved PackagePath as the `PackageIcon`

    eg. <None Include="logo.png" Pack="true" PackagePath="\" PackageIcon="true" />
   -->
  <Target Name="_SetPackageIconByConvention"
          DependsOnTargets="_GetPackageFiles"
          BeforeTargets="GenerateNuspec"
          Condition="'$(PackageIcon)' == ''">
    <ItemGroup>
      <DiscoveredIcon Include="@(_PackageFiles)" Condition="'%(_PackageFiles.PackageIcon)' == 'true'">
        <_PackagePath>%(_PackageFiles.PackagePath)</_PackagePath>
        <_PackagePath Condition="'%(_PackageFiles.PackagePath)' == '/'"></_PackagePath>
      </DiscoveredIcon>
    </ItemGroup>
    <PropertyGroup Condition="'@(DiscoveredIcon)' != ''">
      <PackageIcon>%(DiscoveredIcon._PackagePath)$([System.IO.Path]::GetFileName(%(DiscoveredIcon.Identity)))</PackageIcon>
    </PropertyGroup>
  </Target>