Debian Release Team,

Modern software systems are built by composing compo-nents drawn from large repositories, whose size and com-plexity increase at a fast pace. Maintaining and evolving these software collections is a complex task, and a strict qualification process needs to be enforced to ensure that the modifications accepted into the reference repository do not disrupt its useability. We studied in depth the Debian soft-ware repository, one of the largest and most complex exist-ing ones, which uses several separate repositories to stage the acceptance of new components, and we developed comi-grate, an extremely efficient tool that is able to identify the largest sets of components that can migrate to the ref-erence repository without violating its quality constraints. This tool outperforms significantly existing tools, and pro-vides detailed information that is crucial to understand the reasons why some components cannot migrate. Extensive validation on the Debian distribution has been performed. The core architecture of the tool is quite general, and can be easily adapted to other software repositories