Update-dependencies-internal pipeline cannot handle SDK-only releases

[lbussell]

Related: https://github.com/dotnet/dotnet-docker-internal/issues/5952 [internal link]

The pre-release validation update pipeline runs into an issue with SDK-only releases. Here's what happens:

Let's say we release version 8.0.200, and we follow that up with an SDK-only release of 8.0.201. If we want to test 8.0.201 then we would call the update-dependencies tool would be called with the arguments:

Set-DotNetVersions \
-ProductVersion 8.0 \
-RuntimeVersion 8.0.X \
-AspnetVersion 8.0.X \
-SdkVersion 8.0.201 \
-UseInternalBuild $true \
...

This will cause the SDK pipeline to look for shas from the SDK build staging pipeline given by the argument --internal-base-url=$InternalBaseUrl. Since that build was SDK-only, the pipeline will fail to find any SHAs for the pre-existing ASP.NET and Runtime versions. This causes the pipeline to fail.

The workaround is currently to update dotnet versions manually and push a branch yourself.

For an easy solution, we could potentially add a pipeline parameter for "Is SDK-only release".

[lbussell]

I think one way to resolve this (and how I updated it by hand) is to have a separate base URL for the SDK in manifest.versions.json`. Usually, this value should be the same as the dotnet base URL (it would reference that variable), but it could be updated independently if we want to test a specific SDK-only release of .NET.

[lbussell]

/cc @NikolaMilosavljevic if you have any other input.

[lbussell]

[Triage] We can leave this open as a known-issue. we should wait to fix it until we know we're going to have another SDK-only release.