Foo.rb

def branch_name_for_build
  Fastlane::Actions::GithubApiAction.run(
    server_url: "https://api.github.com",
    api_token: @GITHUB_API_TOKEN,
    http_method: "GET",
    path: "/repos/beachbodydigital/devices-bod-ios/pulls/23",
    error_handlers: {
      '*' => proc do |result|
        raise "This build is from a PR but the request to GitHub's PR API for PR metadata failed."
      end
    }
  ) do |result|
    title = result[:json]['title']
    puts(title) # some-title
    title
  end

branch_name = branch_name_for_build
puts("Building with branch name: '#{branch_name}'") # Building with branch name: '{:status=>200, :body=>"{\"url\":\"https://a...