@yehuda, can you please provide a write-up on how to use this tool? Also, please let me know if any specific test environment needs are there to test this.
Verified in 2.1
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHSA-2016-2815.html
The resharding command parameter should be --num-shards. $ radosgw-admin bucket reshard --bucket=<bucket name> --num-shards=<new shards number>