Add the ability to get a connection by alias from aggregated connections.

Previously it was possible to create a new instance of Predis\Client using
the alias of a single connection in a cluster of connections. Now we added
the ability to do this also when using master/slave replication.

lib/Predis/Client.php

@@ -196,8 +196,8 @@ class Client
     public function getConnection($id = null)
     {
         if (isset($id)) {
-            if (!Helpers::isCluster($this->connection)) {
-                $message = 'Retrieving connections by alias is supported only with clustered connections';
+            if (!Helpers::isAggregated($this->connection)) {
+                $message = 'Retrieving connections by alias is supported only with aggregated connections (cluster or replication)';
                 throw new NotSupportedException($message);
             }
             return $this->connection->getConnectionById($id);

lib/Predis/Helpers.php

@@ -13,6 +13,7 @@ namespace Predis;
 
 use Predis\Network\IConnection;
 use Predis\Network\IConnectionCluster;
+use Predis\Network\IConnectionReplication;
 
 /**
  * Defines a few helper methods.
@@ -21,6 +22,17 @@ use Predis\Network\IConnectionCluster;
  */
 class Helpers
 {
+    /**
+     * Checks if the specified connection represents an aggregation of connections.
+     *
+     * @param IConnection $connection Connection object.
+     * @return Boolean
+     */
+    public static function isAggregated(IConnection $connection)
+    {
+        return $connection instanceof IConnectionCluster || $connection instanceof IConnectionReplication;
+    }
+
     /**
      * Checks if the specified connection represents a cluster.
      *

tests/Predis/ClientTest.php

@@ -385,7 +385,7 @@ class ClientTest extends StandardTestCase
     /**
      * @group disconnected
      * @expectedException Predis\NotSupportedException
-     * @expectedExceptionMessage Retrieving connections by alias is supported only with clustered connections
+     * @expectedExceptionMessage Retrieving connections by alias is supported only with aggregated connections (cluster or replication)
      */
     public function testGetConnectionWithAliasWorksOnlyWithCluster()
     {