Keep only the targeted backend in the replica metadata

toReplicaEntry cloned the source entry and only updated the targeted
backend, so the destination metadata inherited the statuses of the
source's other destinations, frozen at queue time and never refreshed.
Keep the targeted backend alone, copying it since clone() shares
replicationInfo with the source.

Issue: BB-875

Author: maeldonn

lib/models/ObjectQueueEntry.js

@@ -232,9 +232,16 @@ class ObjectQueueEntry extends ObjectMD {
 
     toReplicaEntry(backend) {
         const newEntry = this.clone();
+        // clone() shares replicationInfo with the source: detach before mutating.
+        newEntry.setReplicationInfo(this.getReplicationInfo());
+        const matched = newEntry._findBackend(backend);
         newEntry
             .setAccountId(this.getAccountId())
             .setBucket(this.getReplicationTargetBucket(backend))
+            // Keep only the targeted backend: the other destinations' statuses
+            // describe the source's own replication and would never be
+            // refreshed here.
+            .setReplicationBackends(matched ? [{ ...matched }] : [])
             .setReplicationSiteStatus(backend, 'REPLICA')
             .setReplicationStatus('REPLICA');
         return newEntry;

tests/unit/lib/models/ObjectQueueEntry.spec.js

@@ -144,6 +144,21 @@ describe('ObjectQueueEntry', () => {
             assert.strictEqual(replicaA.getBucket(), 'bucket-a');
             assert.strictEqual(replicaB.getBucket(), 'bucket-b');
         });
+
+        it('toReplicaEntry drops the other destinations statuses', () => {
+            const entry = _makeEntryWithBackends([
+                { site: 'siteA', status: 'PENDING', dataStoreVersionId: '' },
+                { site: 'siteB', status: 'PENDING', dataStoreVersionId: '' },
+            ]);
+
+            const replica = entry.toReplicaEntry({ site: 'siteB' });
+            assert.deepStrictEqual(
+                replica.getReplicationBackends().map(b => b.site), ['siteB']);
+            assert.strictEqual(replica.getReplicationSiteStatus({ site: 'siteB' }), 'REPLICA');
+            assert.strictEqual(replica.getReplicationStatus(), 'REPLICA');
+            assert.strictEqual(entry.getReplicationBackends().length, 2);
+            assert.strictEqual(entry.getReplicationSiteStatus({ site: 'siteB' }), 'PENDING');
+        });
     });
 
     describe('same-site backend disambiguation', () => {