add a class `FrontmatterDefaults` for handling of frontmatter defaults

lib/jekyll.rb

@@ -31,6 +31,7 @@ require 'jekyll/core_ext'
 require 'jekyll/stevenson'
 require 'jekyll/deprecator'
 require 'jekyll/configuration'
+require 'jekyll/frontmatter_defaults.rb'
 require 'jekyll/site'
 require 'jekyll/convertible'
 require 'jekyll/url'

lib/jekyll/configuration.rb

@@ -40,6 +40,8 @@ module Jekyll
 
       'excerpt_separator' => "\n\n",
 
+      'defaults'     => [],
+
       'maruku' => {
         'use_tex'    => false,
         'use_divs'   => false,
@@ -217,6 +219,5 @@ module Jekyll
 
       config
     end
-
   end
 end

lib/jekyll/frontmatter_defaults.rb

@@ -0,0 +1,53 @@
+module Jekyll
+  class Configuration
+    class FrontmatterDefaults
+      def initialize(site)
+        @site = site
+      end
+
+      def find(path, type, setting)
+        value = nil
+        matching_sets(path, type).each do |set|
+          value = set['values'][setting] if set['values'].has_key?(setting)
+        end
+        value
+      end
+
+      def all(path, type)
+        defaults = {}
+        matching_sets(path, type).each do |set|
+          defaults.merge! set['values']
+        end
+        defaults
+      end
+
+      private
+
+      def applies?(scope, path, type)
+        (scope['path'].empty? || path.starts_with?(scope['path'])) && (!scope.has_key?('type') || scope['type'] == type.to_s)
+      end
+
+      def valid?(set)
+        set['scope'].is_a?(Hash) && set['scope'].has_key?('path') && set['values'].is_a?(Hash)
+      end
+
+      def matching_sets(path, type)
+        valid_sets.select do |set|
+          applies?(set['scope'], path, type)
+        end
+      end
+
+      def valid_sets
+        sets = @site.config['defaults']
+        return [] unless sets.is_a?(Array)
+
+        sets.select do |set|
+          unless valid?(set)
+            Jekyll.logger.warn "Default:", "An invalid default set was found"
+          end
+          valid?(set)
+        end
+      end
+    end
+  end
+end

lib/jekyll/site.rb

@@ -369,6 +369,10 @@ module Jekyll
       end
     end
 
+    def frontmatter_defaults
+      @frontmatter_defaults ||= Configuration::FrontmatterDefaults.new(self)
+    end
+
     private
 
     def has_yaml_header?(file)