Migration Plugin

Those tests require 2 snapshots.

Snapshot 1:

• empty repo, no importer, a distributor
• another empty repo (to copy content to later), no importer, a distributor
• rpm-with-modules repo, on_demand importer, a distributor
• rpm-distribution-tree repo, on_demand importer, a distributor
• srpm-unsigned repo, on_demand importer, a distributor

Snapshot 2:

• empty repo and its distributor unchanged
• copy a package to an empty repo, and its distributor unchanged
• rpm-with-modules repo (remove one package, clean orphans), importer feed change, distributor with no changes
• rpm-distribution-tree repo unchanged, its importer unchanged, distributor checksum_type change
• srpm-unsigned repo unchanged, its importer unchanged, distributor relative path change
• rpm-richweak-deps repo (sync, remove one package, no orphan cleanup)