ROS Rolling syncs go automatic with risk-based thresholds

ROS Rolling syncs are moving from manual to automatic. Currently, getting packages from the build farm's testing repository into the main apt archive requires a human on the release team to trigger and announce a sync. That leads to batching delays, single-regression blocking of all packages, and unpredictable timing. The new proposal eliminates the manual gate by making syncs automatic once a candidate batch meets a readiness threshold determined by two factors: batch size and position in the dependency graph. A large, well-tested batch of leaf packages (few downstream dependencies) can sync sooner, while packages high up the dependency chain require more validation and soak time before an automatic sync fires. Most day-to-day updates should reach main faster and on a more predictable schedule, while high-impact packages still get extra scrutiny.

The threshold is dynamic: relaxed now through early next year, then tightened as the M Turtle release (May 2027) approaches, then relaxed again after shipping. The release team will publish numeric thresholds and changes in advance. Co-installation with stable distros (Kilted, Lyrical) on the same system remains supported because Rolling stays on main. Stable distros (Humble, Jazzy, Kilted) are unaffected, and the maintainer release process (via bloom) stays the same. Open questions include the starting batch size and whether to allow an expedite path for urgent fixes. The goal is to decouple release velocity from team bandwidth and tie it to actual package quality.