Mercurial is extensible, and there are many extensions that can be added to it - it would be nice to have these installed along with it. Two possible ways: 1. add use flags to the Mercurial set of flags to indicate these extensions to be downloaded with it, i.e hgforest to add the forest extension OR 2. build a set of ebuilds that can be installed when Mercurial needs them.. The most critical one is the forest extension though as a few open software projects out there needs this feature (openjdk for example)
Forest is third-party extension, all the core extensions are already there. Additionally Forest doesn't have downloadable, versioned tarball. For such extensions it's best to manage them on your own.
I see, thank you.