mepo is a tool, written in Python3 (3.6.0+), to manage (m)ultiple git r(epo)sitories, by attempting to create an illusion of a 'single repository' for multi-repository projects. Please see the Wiki for examples of mepo workflows.
For more about the possible mepo commands, please see the Mepo Commands wiki page.
The SI Team has made a PowerPoint about mepo that can be found here.