An incomplete shard snapshot will prevent a shard from moving away from a node (see `SnapshotInProgressAllocationDecider`). That means that when a shard snapshot completes it may become possible to perform some shard movements that previously were not possible, so we should trigger a reroute to start those movements. AFAICT we do not trigger such a reroute today.
server/src/test/java/org/elasticsearch/snapshots/SnapshotResiliencyTests.java
actionFilters,
                        indexNameExpressionResolver,
                        new DestructiveOperations(settings, clusterSettings)
                    )
                );
                actions.put(
                    PutRepositoryAction.INSTANCE,
                    new TransportPutRepositoryAction(
                        transportService,
                        clusterService,
                        repositoriesService,
                        threadPool,
                        actionFilters,
                        indexNameExpressionResolver
                    )
                );
                actions.put(
                    CleanupRepositoryAction.INSTANCE,
                    new TransportCleanupRepositoryAction(
                        transportService,
                        clusterService,
                        repositoriesService,
                        threadPool,
                        actionFilters,
                        indexNameExpressionResolver
                    )
                );
                actions.put(
                    CreateSnapshotAction.INSTANCE,
                    new TransportCreateSnapshotAction(