Enable debugging by default, allow for more arguments.

Change-Id: I3ceb8caef1c0e2ae844501f4791bb858b8781333
Add further testing based on some data files I had

Since I think we like what it currently produces, these merely check
that the current outputs are what is produced.

Change-Id: If7aab4dcfb7ff6a89f0b34d33bf64f623f14eaca
Extract patchset description to helper.

This is done the same way across all our emitters, so it might as
well be common. This also makes it easier to change.

Change-Id: I0475d9f50f87b87d3e22eb4b7abae692a7716b3e
Remove redundant imports.

Change-Id: If5e4e483a9843f109234e54b219bef99e15f6927
Only hide the commit subject on private repos.

There's no need to hide the fact that the repo has been updated,
nor by whom. Instead just avoid emitting the subject information
for these changes.

Change-Id: Ida1aeac1d203c8211179cda04cd61b6aa10bd524