v8.3.1

• add merge-duplicates option

merge-duplicates specifies that all summary files with the same OS-version/node-version are merged and treated as a single input file. The priority of the merging is similar to Object.assign(final, t1, t2, t3) where t1 represents the first summary file generated, t2 the second, and t3 the last. This is most useful when summaries after t1 contain only the results for a subset of packages in t1. E.g., if only package bcrypt failed in the t1 run then t2 could contain only the results of the bcrypt test and the output would be as if t1 included the t2 bcrypt test results (replacing the failed results in t1).

• added the del method to Grouper