I don't know if I could help you with devstack upgrades. We've performed them one by one (J->K->L->M) in production environment under chef, and on each upgrade we've applied different version of configuration files (there is no 'compatible config' for all versions J through M).
I don't know if I could help you with devstack upgrades. We've performed them one by one (J->K->L->M) in production environment under chef, and on each upgrade we've applied different version of configuration files (there is no 'compatible config' for all versions J through M).