ruby_shebang?

# File lib/bundler/cli/exec.rb, line 88
    def ruby_shebang?(file)
      possibilities = [
        "#!/usr/bin/env ruby\n",
        "#!/usr/bin/env jruby\n",
        "#!/usr/bin/env truffleruby\n",
        "#!#{Gem.ruby}\n",
      ]

      if File.zero?(file)
        Bundler.ui.warn "#{file} is empty"
        return false
      end

      first_line = File.open(file, "rb") {|f| f.read(possibilities.map(&:size).max) }
      possibilities.any? {|shebang| first_line.start_with?(shebang) }
    end