Write out metadata about git repos on disk

Here's a workaround (possibly not optimal, but explain seemed OK and it returned quickly:

launchpad_prod=# select person.name as owner, product.name as project, gitrepository.name as repo from gitrepository,person,product where gitrepository.id = 30355 and gitrepository.owner = person.id and gitrepository.project = product.id;
      owner | project | repo
-----------------+--------------------+--------------------
 ubuntu-security | ubuntu-cve-tracker | ubuntu-cve-tracker
(1 row)

launchpad_prod=# _

But it would certainly be more convenient if this information were closer to hand.

Not clear this is the preferred solution to the problem - let's consider e.g. better query tooling / some kind of convenience tool to fetch the info live - but agree there's a gap there!

In particular, we don't want LP to have to ask turnip to change the description of a large number of repositories when a person or target name changes.