If you use fastlane for your mobile environment and IntelliJ then you must be feeling the pain of opening your
fastlane/Fastfile in IntelliJ and see all without syntax highlights or autocomplete?
That's because it does not have
.rb and so IntelliJ can't understand the language of the file, but there's one simple setup that will fix it:
Settings / File Types
Search for Ruby
Thanks to custom-file-types-in-intellij-idea