GitHub supports ul indenting using one or two spaces but this module requires the Markdown specification of 4 spaces.

[chr15m]

I think it would make sense to ignore the specification and do what GitHub allows since the name of the module is "GitHub Flavoured Markdown".

Test markdown to replicate this bug:

 * First item.
   * First indented item.
   * Second indented item.
 * Second item.
 * Third item.

The sub-list indenting works correctly on GitHub and with the original markdown.pl implementation, but does not work with py-gfm or several other markdown renderers.

[chr15m]

For anybody finding this issue, the python module markdown2 renders lists consistently with GitHub and the original markdown.pl, against the spec.