The job reports all packages, and their dependencies. Right now, it
reports packages that were built only, hence the get_repo_missing name
was fitting. But this will be changed to report *all* packages soon,
therefore call it get_depends.

Related: #38

If there is already a database, it is more interesting to see how the
code would continue building everything in the queue.

Let's keep the data around, so we can discover and fix problems related
to restarts. To remove all bpo server data, just run the testsuite.

Use -a and don't set a postmarketOS mirror, so it builds everything
right now.

Make it easier to find bugs related to not creating a dir in _temp.

Allow changing the postmarketOS mirror on the commandline, so we can
easily use a different value in the testing environment.

This is how I'm currently testing every change locally, first run this
script and then test/curl/push-hook-gitlab.sh. That simulates the
complete chain of events, from a git push event from gitlab to calling
the repo_missing job, to building packages and finally updating the
final repo (last part is currently a stub).