What does features_exclude mean in a features info file? I found this line in the *.info file of one of my feature modules.

features_exclude[field_base][field_block] = field_block


I did find a number of drupal.org issues dealing with this, but no documentation about the intended purpose.

The context of my example does not really matter; I am asking about the general meaning and implications of the features_exclude key.
features_exclude is generated by the Features UI when creating a Feature. It is not created by drush fu FEATURE_NAME. See https://www.drupal.org/node/1064472#comment-7196064.


  The features_exclude lines are purely for the new UI to determine if an auto-detected dependency should be checked or if you have specifically unchecked it.