When you deploy your plugin you get the address, so you know your plugin address, but there are no functions on the contracts (that I can see) that matches repo names with addresses. Is the idea that there would be a subgraph that indexes all the plugins so you cans see whats available?
Subgraph is a key piece here, because there is where Aragon indexes everything so that the UI knows what plugins the DAO has installed, what version, when, etc.
Indeed, that is where all the information will leave. It can be accessed through Aragon's SDK (https://github.com/aragon/sdk)