let run-tests run optional code coverage tests.
to enable, set env var TEST_COVERAGE to non-empty string. run-tests will
print report after running.
after coverage run, file tests/.coverage will contain coverage data. use
tests/coverage.py to get more info, like annotated source code.
adding foo
pushing to ../2
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files