IBCData requires knowledge of the source branch of dependency flow

[mmitche]

When IBC data is enabled in roslyn, it looks up the opiimization data based on the source branch that is being built, and finds the most relevant data. This means if we're building 17.4, it'll go find the 17.4 data.

This won't work in the VMR since the source branch wouldn't match roslyn's branches. We will somehow need to know and expose the source branch of flow to the build in these cases.

[premun]

Can we just mandate that they have the version stored in a file on the branch and change it when they snap?

[mmitche]

We could, but my guess is that it will be wrong at times.