Hey,

As has happened before in the past, at the moment we're not getting
emails to guix-commits for the main guix.git repository. This impacts
the data service instances as they use these emails to know when there
are new revisions to process.

I've now added the ability to configure the data service to poll the
repository for changes and I've enabled this on both data.guix.gnu.org
and data.qa.guix.gnu.org, which should mean they'll be shortly back up
to date.

This sounds easy, but it was a little tricky to implement, as I didn't
want to remove the email feature in favour of polling, at least not
yet. It's also had a large impact on data.qa.guix.gnu.org, as now it's
learned about lots of older branches that it didn't know about before.

Chris