In GitLab, How Do You Find Only Files (not folders or projects) That Have “foo” in Their Content and Have File Extensions of .bar?

Problem scenario
You are using the GitLab GUI. You want to find files that end with .bar and have the patter "foo" in the content. How do you find them?

Solution
Use the Search feature. Use this as the search term for a given Group in GitLab (with "Any" for the "Project"):

foo extension:bar

(Do not use ".bar".)

The source of this is https://docs.gitlab.com. "Finding any file with the .yaml extension: extension:yaml" taken from https://docs.gitlab.com/ee/user/search/advanced_search.html