Introduce distinction between preview/productive site generation

Posts which contain the YAML attribute `published: false` are usually
not generated by Jekyll. With this patch they can be previewed just
like published posts on localhost using `rake watch`or `rake preview`.

NOTICE: Before pushing to the productive environment, use `rake generate`
to update the public directory and remove posts which are flagged not to be
published.

Rakefile

@@ -59,7 +59,7 @@ task :watch do
   raise "### You haven't set anything up yet. First run `rake install` to set up an Octopress theme." unless File.directory?(source_dir)
   puts "Starting to watch source with Jekyll and Compass."
   system "compass compile --css-dir #{source_dir}/stylesheets" unless File.exist?("#{source_dir}/stylesheets/screen.css")
-  jekyllPid = Process.spawn("jekyll --auto")
+  jekyllPid = Process.spawn({"OCTOPRESS_ENV"=>"preview"}, "jekyll --auto")
   compassPid = Process.spawn("compass watch")
 
   trap("INT") {
@@ -75,7 +75,7 @@ task :preview do
   raise "### You haven't set anything up yet. First run `rake install` to set up an Octopress theme." unless File.directory?(source_dir)
   puts "Starting to watch source with Jekyll and Compass. Starting Rack on port #{server_port}"
   system "compass compile --css-dir #{source_dir}/stylesheets" unless File.exist?("#{source_dir}/stylesheets/screen.css")
-  jekyllPid = Process.spawn("jekyll --auto")
+  jekyllPid = Process.spawn({"OCTOPRESS_ENV"=>"preview"}, "jekyll --auto")
   compassPid = Process.spawn("compass watch")
   rackupPid = Process.spawn("rackup --port #{server_port}")
 

plugins/preview_unpublished.rb

@@ -0,0 +1,45 @@
+# Monkeypatch for Jekyll
+# Introduce distinction between preview/productive site generation
+# so posts with YAML attribute `published: false` can be previewed
+# on localhost without being published to the productive environment.
+
+module Jekyll
+
+  class Site
+    # Read all the files in <source>/<dir>/_posts and create a new Post
+    # object with each one.
+    #
+    # dir - The String relative path of the directory to read.
+    #
+    # Returns nothing.
+    def read_posts(dir)
+      base = File.join(self.source, dir, '_posts')
+      return unless File.exists?(base)
+      entries = Dir.chdir(base) { filter_entries(Dir['**/*']) }
+
+      # first pass processes, but does not yet render post content
+      entries.each do |f|
+        if Post.valid?(f)
+          post = Post.new(self, self.source, dir, f)
+
+          # Monkeypatch:
+          # On preview environment (localhost), publish all posts
+          if ENV.has_key?('OCTOPRESS_ENV') && ENV['OCTOPRESS_ENV'] == 'preview'
+            post.published = true
+          end
+
+          if post.published && (self.future || post.date <= self.time)
+            self.posts << post
+            post.categories.each { |c| self.categories[c] << post }
+            post.tags.each { |c| self.tags[c] << post }
+          end
+        end
+      end
+
+      self.posts.sort!
+
+      # limit the posts if :limit_posts option is set
+      self.posts = self.posts[-limit_posts, limit_posts] if limit_posts
+    end
+  end
+end