[@dwijnand]: http://github.com/dwijnand
  [1828]: https://github.com/sbt/sbt/issues/1828
  [1922]: https://github.com/sbt/sbt/pull/1992

### Fixes with compatibility implications

### Improvements

### Bug fixes

- Fix `crossScalaVersions` default, now correctly derives from the configured `scalaVersion`. [#1828][1828]/[#1992][1992] by [@dwijnand][@dwijnand]