Code-listings generated by lore2sphinx should include line-numbers

[Screwtape]

exarkun, in ticket #4566 comment 5:

One thing I noticed while reviewing this, though, is that code listings no longer have line numbers. Could you file a ticket for that?

It  looks like Lore puts line-numbers on <pre class="python"> blocks, but not on python-interpreter or shell blocks.

From what I can see  in the Sphinx docs, this can be enabled on a per-document basis with a fragment of code like:

.. highlight:: python
   :linenothreshold: 1

...but it would be even better if that could be set as a project-wide setting; I'm not sure if that's possible.

[khorn]

This can also be set for individual code blocks like so:

.. code-block:: python
   :linenos:

   Code goes here...

As far as a project-wide setting for :linenothreshold:, I don't think this is possible (at least not yet).

Also, I believe the "highlight" directive only works on blocks that begin with "::", rather than ".. code-block", but I'm not positive about that.

[khorn]

After some investigation, it seems that the "linenothreshold" option of the "highlight" directive only works on automatically-highlighted blocks, which as far as I can tell means blocks beginning with "::" and blocks included with the "literalinclude" directive.

Blocks created with "code-block" directives do not recognize the "linenothreshold" option. Line numbers can be enabled on them, but need to be done so individually.

It shouldn't be too difficult to get lore2sphinx to generate the proper options for the "code-block" directives to show line numbers if we decide we want it to.