FileSystemHelper is a linked file in GitVersion.Testing, but now it's also coming in as a proper reference in GitVersion.Core. Dropping the linked file sorts the warning:

The type 'FileSystemHelper' in '/Users/runner/work/GitVersion/GitVersion/src/GitVersion.Testing/../GitVersion.Core/Helpers/FileSystemHelper.cs' conflicts with the imported type 'FileSystemHelper' in 'GitVersion.Core, Version=6.3.1.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in '/Users/runner/work/GitVersion/GitVersion/src/GitVersion.Testing/../GitVersion.Core/Helpers/FileSystemHelper.cs'.

Author: 9swampy

src/GitVersion.Testing/GitVersion.Testing.csproj

@@ -8,9 +8,6 @@
         <PackageReference Include="System.IO.Abstractions" />
         <PackageReference Include="System.Reflection.Metadata" />
     </ItemGroup>
-    <ItemGroup>
-        <Compile Include="..\GitVersion.Core\Helpers\FileSystemHelper.cs" Link="Helpers\FileSystemHelper.cs" />
-    </ItemGroup>
     <ItemGroup>
         <InternalsVisibleTo Include="GitVersion.BuildAgents.Tests" />
         <InternalsVisibleTo Include="GitVersion.Configuration.Tests" />