### Proposal <!-- Use this section to explain the feature and how it will work. It can be helpful to add technical details, design proposals, and links to related epics or issues. --> Provide the ability to pass in a branch to GET /projects/:id/languages to get back the programming languages in use on that particular branch. https://docs.gitlab.com/ee/api/projects.html#languages Our organization is looking to setup standards around programming language usage and if we wait until teams merge into the mainline (default) branch, our feedback loop is slower. This issue is similar where other customers cannot see language break down by branch in the UI either - https://gitlab.com/gitlab-org/gitlab/-/issues/25428 <!-- Label reminders Use the following resources to find the appropriate labels: - https://gitlab.com/gitlab-org/gitlab/-/labels - https://about.gitlab.com/handbook/product/categories/features/ -->