DM-3371 adds the --rerun option to command line tasks. The help for this option reads:
rerun name: sets OUTPUT to ROOT/rerun/OUTPUT; optionally sets ROOT to ROOT/rerun/INPUT
While essentially correct, that's not particularly helpful in understanding what's actually going on here. A motivation and description of this functionality is available in
RFC-95: please ensure that, or some variation of it, is included in the stack documentation.