Before this change, this module determined if a terragrunt.hcl file was a parent or not by examining if it had a terraform.source field in it's hcl. This is not enough, as some actual (non-parent) modules may leave this field blank, which assumes a default of terraform { source = "." }.
This change now also looks if there is an includes block present, which is a definite signal that a module is not a parent.