Generate coverage report from unit and integration tests

[pederhan]

It would be useful to generate a coverage report from a combination of unit tests and the integration test suite. That would give us an overview of commands that are in need of better testing.

Seeing as the breakage fixed in #322 slipped under the radar, it means that command is neither tested by unit tests or integration tests. Having proper coverage reporting would have warned us of that command (and others) not being tested.