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.
merge: warning: conflicts during merge
merging a
merging a failed!
e7fe8eb3e180+0d24b7662d3e+ tip
something else
=======
something
M a