Support post_defaults section in _config.yml, typically used to set a…

… default layout for posts.

Based on code by geekq: http://github.com/geekq/jekyll/commit/2d4274ecbc97a0810a51a55f04aa9d9b53561de8

README.textile

@@ -238,6 +238,15 @@ Parameters set in a configuration file override the default values. Parameters
 set using command line options override both the default values and those set
 in a configuration file.
 
+Additionally, you can set defaults for the post data blocks. For example, you
+can set the default layout for posts, so you don't have to specify it in every
+post:
+
+  post_defaults:
+    layout: post
+
+Any values set in the actual post will override these defaults.
+
 h2. Data
 
 Jekyll traverses your site looking for files to process. Any files with YAML
@@ -329,6 +338,9 @@ h3. Predefined Global Variables
     If set, this specifies the layout file to use. Use the layout file
     name without file extension. Layout files must be placed in the
     <code>_layouts</code> directory.
+
+    A default layout for posts can be set in the configuration file.
+    See above.
 
 h3. Predefined Post Variables
 

lib/jekyll/convertible.rb

@@ -21,7 +21,8 @@ def read_yaml(base, name)
       if self.content =~ /^(---\s*\n.*?)\n---\s*\n/m
         self.content = self.content[($1.size + 5)..-1]
 
-        self.data = YAML.load($1)
+        self.data ||= {}
+        self.data = self.data.merge(YAML.load($1))
       end
     end
 

lib/jekyll/post.rb

@@ -42,6 +42,7 @@ def initialize(site, source, dir, name)
       self.topics = parts.size > 1 ? parts[0..-2] : []
 
       self.process(name)
+      self.data = self.site.post_defaults.dup
       self.read_yaml(@base, name)
 
       if self.data.has_key?('published') && self.data['published'] == false

lib/jekyll/site.rb

@@ -2,7 +2,8 @@ module Jekyll
 
   class Site
     attr_accessor :config, :layouts, :posts, :categories
-    attr_accessor :source, :dest, :lsi, :pygments, :permalink_style, :permalink_date, :sass
+    attr_accessor :source, :dest, :lsi, :pygments, :permalink_style, :permalink_date,
+                  :sass, :post_defaults
 
     # Initialize the site
     #   +config+ is a Hash containing site configurations details
@@ -17,6 +18,7 @@ def initialize(config)
       self.pygments        = config['pygments']
       self.permalink_style = config['permalink'].to_sym
       self.permalink_date  = config['permalink_date'] && config['permalink_date'].sub(%r{\A/?(.*)/?\Z}, '/\1/')
+      self.post_defaults   = config['post_defaults'] || {}
 
       self.reset
       self.setup