Add :knitr filter

Rules

@@ -23,6 +23,9 @@ compile '/blog/' do
 end
 
 compile '/blog/*' do
+  if item[:extension] == 'Rmd'
+    filter :knitr
+  end
   filter :pandoc, ['mathjax']
   filter :colorize_syntax, :default_colorizer => :pygmentsrb
   layout 'post'

lib/default.rb

@@ -10,3 +10,16 @@ def ShortBlogName(item)
   title = item[item.attributes.has_key?(:short_url) ? :short_url : :title]
   title.split(%r{\W+}).join('_')
 end
+
+
+class KnitrFilter < Nanoc::Filter
+  identifier :knitr
+
+  def run(content, params={})
+    # Escape content to fit inside R's double quotes inside bash single quotes.
+    escaped_content = content.gsub(%r{\\}, "\\\\\\").gsub(%r{"}, '\"').gsub(%r{'}, "'\"'\"'").gsub(%r{\n}, "\\n")
+    command = ('Rscript -e \'library(knitr); cat(knit(quiet=TRUE, text="' +
+               escaped_content + '"))\'')
+    `#{command}`
+  end
+end

nanoc.yaml

@@ -1,7 +1,7 @@
 # A list of file extensions that nanoc will consider to be textual rather than
 # binary. If an item with an extension not in this list is found,  the file
 # will be considered as binary.
-text_extensions: [ 'coffee', 'css', 'erb', 'haml', 'handlebars', 'hb', 'htm', 'html', 'js', 'less', 'markdown', 'md', 'ms', 'mustache', 'pandoc', 'php', 'rb', 'sass', 'scss', 'txt', 'xhtml', 'xml' ]
+text_extensions: [ 'coffee', 'css', 'erb', 'haml', 'handlebars', 'hb', 'htm', 'html', 'js', 'less', 'markdown', 'md', 'ms', 'mustache', 'pandoc', 'php', 'Rmd', 'rb', 'sass', 'scss', 'txt', 'xhtml', 'xml' ]
 
 # The path to the directory where all generated files will be written to. This
 # can be an absolute path starting with a slash, but it can also be path