In the inner loop, we operate on version-language pairs. These are currently only joined in the type system via tuples, or not at all. By introducing theBuildMetadata class, we make the link explicit.

My intent is to (later) add further attributes toBuildMetadata (e.g. the directory paths), makingBuildMetadata a data-only class that performs no actions, withDocBuilder performing the actual build. For example,DocBuilder.html_only could be fully merged intoBuildMetadata.

A