checkCompatibility

The Manifest gate of the service owner (project ':x', as a failure names it): compares the service's current Manifest with its committed baseline (ManifestCompatibility, Baseline) and writes the classified changes to report. Fails when there is no baseline; when a change breaks the contract within the baseline's compatibility line (the service's major version is the line's, and no pre-release keeps it open, Baseline.allowsBreaking), listing each; and when the baseline is not the Manifest this build produces, its version aside, or not of the service's major: every change is recorded, so the baseline's diff in review shows what the clients will see. Each failure names UPDATE_BASELINE_TASK. Returns the number of additive changes.