allow passing extra args to pandoc filters

use:

    cell.source | markdown2latex(['--no-wrap'])

to disable text wrapping

IPython/nbconvert/filters/markdown.py

@@ -45,7 +45,7 b' class NodeJSMissing(ConversionException):'
     """Exception raised when node.js is missing."""
     pass
 
-def markdown2latex(source):
+def markdown2latex(source, extra_args=None):
     """Convert a markdown string to LaTeX via pandoc.
 
     This function will raise an error if pandoc is not installed.
@@ -61,7 +61,7 b' def markdown2latex(source):'
     out : string
       Output as returned by pandoc.
     """
-    return pandoc(source, 'markdown', 'latex')
+    return pandoc(source, 'markdown', 'latex', extra_args=extra_args)
 
 
 @undoc
@@ -155,9 +155,10 b' def markdown2html_mistune(source):'
     """Convert a markdown string to HTML using mistune"""
     return MarkdownWithMath(renderer=IPythonRenderer()).render(source)
 
-def markdown2html_pandoc(source):
+def markdown2html_pandoc(source, extra_args=None):
     """Convert a markdown string to HTML via pandoc"""
-    return pandoc(source, 'markdown', 'html', extra_args=['--mathjax'])
+    extra_args = extra_args or ['--mathjax']
+    return pandoc(source, 'markdown', 'html', extra_args=extra_args)
 
 def _find_nodejs():
     global _node
@@ -188,7 +189,7 b" def markdown2html_marked(source, encoding='utf-8'):"
 # The mistune renderer is the default, because it's simple to depend on it
 markdown2html = markdown2html_mistune
 
-def markdown2rst(source):
+def markdown2rst(source, extra_args=None):
     """Convert a markdown string to ReST via pandoc.
 
     This function will raise an error if pandoc is not installed.
@@ -204,7 +205,7 b' def markdown2rst(source):'
     out : string
       Output as returned by pandoc.
     """
-    return pandoc(source, 'markdown', 'rst')
+    return pandoc(source, 'markdown', 'rst', extra_args=extra_args)
 
 def _verify_node(cmd):
     """Verify that the node command exists and is at least the minimum supported

IPython/nbconvert/filters/tests/test_markdown.py

@@ -11,6 +11,7 b' from IPython.testing import decorators as dec'
 from ...tests.base import TestsBase
 from ..markdown import markdown2latex, markdown2html, markdown2rst
 
+from jinja2 import Environment
 
 class TestMarkdown(TestsBase):
 
@@ -47,6 +48,26 b' class TestMarkdown(TestsBase):'
         for index, test in enumerate(self.tests):
             self._try_markdown(markdown2latex, test, self.tokens[index])
 
+    @dec.onlyif_cmds_exist('pandoc')
+    def test_pandoc_extra_args(self):
+        # pass --no-wrap
+        s = '\n'.join([
+            "#latex {{long_line | md2l(['--no-wrap'])}}",
+            "#rst {{long_line | md2r(['--columns', '5'])}}",
+        ])
+        long_line = ' '.join(['long'] * 30)
+        env = Environment()
+        env.filters.update({
+            'md2l': markdown2latex,
+            'md2r': markdown2rst,
+        })
+        tpl = env.from_string(s)
+        rendered = tpl.render(long_line=long_line)
+        _, latex, rst = rendered.split('#')
+        
+        self.assertEqual(latex.strip(), 'latex %s' % long_line)
+        self.assertEqual(rst.strip(), 'rst %s' % long_line.replace(' ', '\n'))
+
     def test_markdown2html(self):
         """markdown2html test"""
         for index, test in enumerate(self.tests):