Why have I got a ‘.NETCore50’ and a ‘netcore50’ folder in my nuget package?

I recently posted on how we were versioning our Nuget packages as part of a release pipeline. In test we noticed that the packages being produced by this process has an extra folder inside them.

We expected there to be a netcore50 folder, but not a .NETCore50 folder. Strangely if we build the package locally we only saw the expect netcore50 folder. The addition of this folder did not appear to be causing any problem, but I did want to find out why it had appeared and remove it as it was not needed.

Turns out the issue was the version of Nuget.exe, the automatically installed version on the on-prem TFS build agent was 3.2, my local copy 3.4. As soon as I upgraded the build box’s nuget.exe version to 3.4 the problem went away