Ticket Duplication Plugin
This plug-in adds the capability of duplicating tickets to other tickets using three custom fields: dup_of, dups, and dup_count. Changes in the master ticket are reflected to the slave tickets and vice versa.
If you have any issues, create a new ticket.
Download the zipped source from here.
fix version string
make a note about the version; avoids code duplication
plugin works with 0.11 too