Create a Repo for "everything private" or "everything public", or "all my work stuff" etc.
Adds delete functionality from java.util.Map to IRepo.
Content Ids are aliases for content.
A virtual repo is a way to package up a piece of a repository and ship it around as content addressable binary data.
A Repo is a binding between a content id scheme and one or more key value stores for binary data.
Caches its content in a
|LazyCa<T extends HasContentId>|
thrown when something goes wrong with resolving content.