add a custom header clients can use to skip a n additional propset request

lib/connector/sabre/file.php

@@ -52,6 +52,12 @@ class OC_Connector_Sabre_File extends OC_Connector_Sabre_Node implements Sabre_D
 		
 		// rename to correct path
 		\OC\Files\Filesystem::rename($partpath, $this->path);
+		
+		//allow sync clients to send the mtime along in a header
+		$mtime = OC_Request::hasModificationTime();
+		if ($mtime !== false) {
+			\OC\Files\Filesystem::touch($this->path,$mtime);
+		}
 
 		return OC_Connector_Sabre_Node::getETagPropertyForPath($this->path);
 	}

lib/request.php

@@ -149,4 +149,16 @@ class OC_Request {
 			return 'gzip';
 		return false;
 	}
+	
+	/**
+	 * @brief Check if the requester sent along an mtime
+	 * @returns false or an mtime
+	 */
+	static public function hasModificationTime () {
+		if (isset($_SERVER['HTTP_X_OC_MTIME'])) {
+			return $_SERVER['HTTP_X_OC_MTIME'];
+		} else {
+			return false;
+		}
+	}
 }