I'm considering going all in with Directory.Build.props and adding another one under the Source directory to configure assembly signing, turning on xml doc generation and configuring source link. Perhaps even another one under Tests to add xunit etc.

Looks good to me! Definitely cleans up a lot of double-ups having a global Directory.Build.props.

Regarding having additional ones under tests and source, I guess it depends whether there will be more projects under those folders or whether the idea is to bring all non-specific configuration out of the single .csproj files.

That said, I'd probably still do it because there is still a chance we might have additional projects later on - whether that be we have separate projects for the extended schema.org types and then require splitting the tests into separate projects for each. 🙂

Regarding having additional ones under tests and source, I guess it depends whether there will be more projects under those folders or whether the idea is to bring all non-specific configuration out of the single .csproj files.

I guess it doesn't matter in this one. I have other projects where it will. I try to keep them all consistent though.

Turns out you have to add a nasty <Import> if you want to use multiple nested Directory.Build.props files. I'll do it in another PR.