add some comment

models/action.go

@@ -22,8 +22,8 @@ const (
 // Action represents user operation type and information to the repository.
 type Action struct {
 	Id          int64
-	UserId      int64 // Receiver user id.
-	OpType      int
+	UserId      int64  // Receiver user id.
+	OpType      int    // Operations: CREATE DELETE STAR ...
 	ActUserId   int64  // Action user id.
 	ActUserName string // Action user name.
 	RepoId      int64