To allow generic manifest walking, we define an interface method of
`References` that returns the referenced items in the manifest. The
current implementation does not return the config target from schema2,
making this useless for most applications.
The garbage collector has been modified to show the utility of this
correctly formed `References` method. We may be able to make more
generic traversal methods with this, as well.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
Until we have some experience hosting foreign layer manifests, the Hub
operators wish to limit foreign layers on Hub. To that end, this change
adds registry configuration options to restrict the URLs that may appear
in pushed manifests.
Signed-off-by: Noah Treuhaft <noah.treuhaft@docker.com>
