Scalafmt cannot run when buildRoots is set

[mattfirtion]

When a buildRoot array is set in .scala-steward.conf and scalafmt is upgraded, Scala Steward tries to run scalafmt --non-interactive from the root of the repository instead of the buildRoot, where .scalafmt.conf most likely lives.

2024-05-20 20:35:48,592 WARN  Post-update hook failed
  org.scalasteward.core.io.process$ProcessFailedException: '"SBT_OPTS=-Xmx2048m -Xss8m -XX:MaxMetaspaceSize=512m" scalafmt --non-interactive' exited with code 16.
  error: missing Scalafmt configuration file.

[fthomas]

Thanks for the report, @mattfirtion!

This points to the core of the problem:

Post-update hook failed

Post-update hooks are currently run at the repo level and not the buildRoot level. To change that, we would probably need to store in which buildRoot we found which dependencies (i.e. changing the type of RepoCache#dependencyInfos).