[seL4] question about repo

This is slightly tangential to sel4.. but.. sel4 uses "repo" to tie together projects that span multiple github repos. I'm really unclear on the proper workflow for using repo. I would like to keep my local patches (and be able to pull down updates from the master repositories), and I would like to pick patches to contribute back. What would the normal flow for these be? Should I be forking each github project that I work with and then fork a master "repo" project to reference my versions, somehow?

Is there a good online guide that covers this?

Tim