def show_coverage
      unless @project.nil?
        line = "## Code coverage\n"
        line << total_coverage_markdown
        line << modified_files_coverage_table
        line << '> Powered by [Slather](https://github.com/SlatherOrg/slather)'
        markdown line
      end
    end
def show_coverage
      unless @project.nil?
        line = "## Code coverage\n"
        line << total_coverage_markdown
        line << modified_files_coverage_table
        line << '> Powered by [Slather](https://github.com/SlatherOrg/slather)'
        markdown line
      end
    end
Show a header with the total coverage and coverage table
 @return [Array<String>]