One way to solve your problem I can think now is to send the diff of each repo as an email attachment because the plugin was not designed to work with multiple repositories. Following is an example of how to send the diff as email (taken from plugin docs):
This message was sent by Atlassian Jira (v7.11.2#711002-sha1:fdc329d)
You received this message because you are subscribed to the Google Groups "Jenkins Issues" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [hidden email].
For more options, visit https://groups.google.com/d/optout.