He's not dead, he's resting
Path and installable-to dependencies
Path dependencies are fairly simple:
cat/pkg::/ will match
cat/pkg installed at root
/. A full path can be used too, so
cat/pkg::/var/mychroot will work (as well as anything involving non-/ roots works, anyway…).
Installable-to dependencies take a bit more explaining. There are two kinds of installable-to dependency: repository and path. An installable-to-repository dependency looks like
cat/pkg::repo? and is matched by any
cat/pkg that could be installed to the repository named
repo. An installable-to-path dependency looks like
cat/pkg::/? and is matched by any
cat/pkg that could be installed to any repository with root
Installable-to dependencies will not match masked packages. To specify “packages that would be installable, ignoring masks”, use a double question mark, like
cat/pkg::/??. At present the double question mark ignores all masks, even those that cannot be overridden (unsupported EAPI, unavailable or unwritten). This may change to only include overridable masks; I’m not sure which is better behaviour yet.