When running with ONLY=X it would be useful to allow the subtest(s) to be run multiple times in order to more efficiently reproduce intermittent test failures, or ensure that they are fixed.

I think something like ONLY_REPEAT=N to cause tests specified with ONLY= to be run N times would be useful. This is not as useful for cases when the whole test script is run, since that can just be run multiple times in a row (possibly in parallel) as each run would take a long time to complete anyway.

It looks like the right place to add this logic would be in run_test() or run_one_logged() (which would need to log the output from each repetition separately).