Only capture operationTime from first aggregate

Author: jmikola

src/Operation/Watch.php

@@ -205,7 +205,6 @@ final public function commandStarted(CommandStartedEvent $event)
             return;
         }
 
-        $this->operationTime = null;
         $this->isFirstBatchEmpty = false;
     }
 
@@ -218,7 +217,9 @@ final public function commandSucceeded(CommandSucceededEvent $event)
 
         $reply = $event->getReply();
 
-        if (isset($reply->operationTime) && $reply->operationTime instanceof TimestampInterface) {
+        /* Note: the spec only refers to collecting an operation time from the
+         * "original aggregation", so only capture it if we've not already. */
+        if (!isset($this->operationTime) && isset($reply->operationTime) && $reply->operationTime instanceof TimestampInterface) {
             $this->operationTime = $reply->operationTime;
         }