sys-fs/archfs is quite old in the Portage tree.
In the mean time it has changed its name to rdiff-backup-fs and reached version 1.0.0. It would be great to see this change in the Portage tree as well.
The dependancies of the package seem to have stayed the same.
+*rdiff-backup-fs-1.0.0 (17 Jun 2013)
+ 17 Jun 2013; Sergey Popov <email@example.com>
+ +rdiff-backup-fs-1.0.0.ebuild, +metadata.xml:
+ Initial commit, wrt bug #457184
As original archfs is abandoned upstream, i have masked it in tree, CCing treecleaners