When a datasource uses the 'merge' registryStrategy (e.g. maven),
mergeRegistries() tags each release with the registryUrl of the repo
that actually reported it. postprocessRelease() ignored this and used
the first configured/default registryUrl instead, causing the Maven
datasource to probe the wrong repository for release verification.
If the artifact didn't exist in that first repo, the release was
wrongly rejected and no update was proposed, even though a valid
release existed in another configured repository.
Tiago Novo