You can specify behaviors on a major-mode basis by customizing the
variable fcm-behavior-modes. This variable must be a list of
specifications of the form ‘(mode :key value ...)’.
mode is a symbol naming a major-mode (without the -mode)
postfix. The available keys are the same as before (see File Name Based Behaviors)
By default, FCM disqualifies text, ChangeLog, outline and fundamental files.