def add_permalink_suffix(template, permalink_style)
      template = template.dup

      case permalink_style
      when :pretty
        template << "/"
      when :date, :ordinal, :none
        template << ":output_ext"
      else
        template << "/" if permalink_style.to_s.end_with?("/")
        template << ":output_ext" if permalink_style.to_s.end_with?(":output_ext")
      end

      template
    end
def add_permalink_suffix(template, permalink_style)
      template = template.dup

      case permalink_style
      when :pretty
        template << "/"
      when :date, :ordinal, :none
        template << ":output_ext"
      else
        template << "/" if permalink_style.to_s.end_with?("/")
        template << ":output_ext" if permalink_style.to_s.end_with?(":output_ext")
      end

      template
    end
Add an appropriate suffix to template so that it matches the specified
 permalink style.

 template - permalink template without trailing slash or file extension
 permalink_style - permalink style, either built-in or custom

 The returned permalink template will use the same ending style as
 specified in permalink_style.  For example, if permalink_style contains a
 trailing slash (or is :pretty, which indirectly has a trailing slash),
 then so will the returned template.  If permalink_style has a trailing
 ":output_ext" (or is :none, :date, or :ordinal) then so will the returned
 template.  Otherwise, template will be returned without modification.

 Examples:
   add_permalink_suffix("/:basename", :pretty)
   # => "/:basename/"

   add_permalink_suffix("/:basename", :date)
   # => "/:basename:output_ext"

   add_permalink_suffix("/:basename", "/:year/:month/:title/")
   # => "/:basename/"

   add_permalink_suffix("/:basename", "/:year/:month/:title")
   # => "/:basename"

 Returns the updated permalink template