Share dev caching implementation between task and server.

Lets have the server and the Rake task go through the same ropes, so we can
share all the file lookup, adding, and deleting code.

railties/lib/rails/commands/server.rb

@@ -2,6 +2,7 @@ require 'fileutils'
 require 'optparse'
 require 'action_dispatch'
 require 'rails'
+require 'rails/dev_caching'
 
 module Rails
   class Server < ::Rack::Server
@@ -100,12 +101,8 @@ module Rails
     private
 
       def setup_dev_caching
-        return unless options[:environment] == "development"
-
-        if options[:caching] == false
-          delete_cache_file
-        elsif options[:caching]
-          create_cache_file
+        if options[:environment] == "development"
+          Rails::DevCaching.enable_by_argument(options[:caching])
         end
       end
 
@@ -116,14 +113,6 @@ module Rails
         puts "=> Run `rails server -h` for more startup options"
       end
 
-      def create_cache_file
-        FileUtils.touch("tmp/caching-dev.txt")
-      end
-
-      def delete_cache_file
-        FileUtils.rm("tmp/caching-dev.txt") if File.exist?("tmp/caching-dev.txt")
-      end
-
       def create_tmp_directories
         %w(cache pids sockets).each do |dir_to_make|
           FileUtils.mkdir_p(File.join(Rails.root, 'tmp', dir_to_make))

railties/lib/rails/dev_caching.rb

@@ -0,0 +1,40 @@
+module Rails
+  module DevCaching # :nodoc:
+    class << self
+      FILE = 'tmp/caching-dev.txt'
+
+      def enable_by_file
+        FileUtils.mkdir_p('tmp')
+
+        if File.exist?(FILE)
+          delete_cache_file
+          puts 'Development mode is no longer being cached.'
+        else
+          create_cache_file
+          puts 'Development mode is now being cached.'
+        end
+
+        FileUtils.touch 'tmp/restart.txt'
+      end
+
+      def enable_by_argument(caching)
+        FileUtils.mkdir_p('tmp')
+
+        if caching
+          create_cache_file
+        elsif caching == false && File.exist?(FILE)
+          delete_cache_file
+        end
+      end
+
+      private
+        def create_cache_file
+          FileUtils.touch FILE
+        end
+
+        def delete_cache_file
+          File.delete FILE
+        end
+    end
+  end
+end

railties/lib/rails/tasks/dev.rake

@@ -1,16 +1,8 @@
+require 'rails/dev_caching'
+
 namespace :dev do
   desc 'Toggle development mode caching on/off'
   task :cache do
-    FileUtils.mkdir_p('tmp')
-
-    if File.exist? 'tmp/caching-dev.txt'
-      File.delete 'tmp/caching-dev.txt'
-      puts 'Development mode is no longer being cached.'
-    else
-      FileUtils.touch 'tmp/caching-dev.txt'
-      puts 'Development mode is now being cached.'
-    end
-
-    FileUtils.touch 'tmp/restart.txt'
+    Rails::DevCaching.enable_by_file
   end
 end