Prototype better logging for parallel processing #10
Description
Right now, output is generated when an action has completed / an artefact is updated.
Ideally, we would write the action when it is started instead. However, that would result in interleaved output in case of parallel processing.
Consider alternate logging strategies, for example where the actual output is (temporarily) stored in a (per artefact) logfile, which may be printed to stdout only in case of failure.