sbt 0.13 will be able to automatically configure scaladoc to link to external sites (via
SI-191) for managed dependencies if those dependencies have a particular property in their pom.xml. This property name is info.apiURL and its value should be the base URL for the API docs for that module version.
So, the pom.xml for scala-library should have a section like:
<properties> <info.apiURL>http://www.scala-lang.org/api/2.10.0/</info.apiURL> </properties>