Mention in Group Specification section that groups w/o includes get p…
…opulated with all Which points out the usefulness of the 'add_items' method.
|@@ -368,6 +368,10 @@ Each option can be a an arrayref|
|or a string which will be converted to|
|an arrayref with a single element.|
|+Specifications that only have C<exclude> and/or C<exclude_groups>|
|+will first be filled with all known items.|
|+(This is where L</add_items> comes in.)|