Intellij IDEA (Community and Ultimate) plugin that adds icons for files like Travis YML, Appveyor YML, Git sub-modules, etc.
You can also register your own icons in order to override file icons, but also all IDE icons (including toolbars, menus, etc.). It works with all JetBrains products like IntelliJ (ultimate and community), PyCharm, WebStorm, DataGrip, etc.
To get started with this plugin, please see this guide.
Please see modified_external_code.
Download plugin from the JetBrains marketplace or via your IDE: File, Settings..., Plugins, Marketplace.