Per-package metadata. The optional 4th element marks an R-core / base package: for these the version keys are the R releases the package shipped with core R, so the set of versions is exactly its core-R history.
Per-package metadata. The optional 4th element marks an R-core / base package: for these the version keys are the R releases the package shipped with core R, so the set of versions is exactly its core-R history.