`rake restart` should work without a `tmp` folder

In restart.rake, the creation of tmp/restart.txt
would fail if the tmp folder does not exist in the
app. This is a problem because apps cloned using
git would not have the tmp folder, as the folder is
in .gitignore. This commit creates the tmp folder
if it does not exist.

Fixes #20299

[Yoong Kang Lim, Sunny Juneja]

railties/lib/rails/generators/rails/app/templates/bin/setup

@@ -25,5 +25,5 @@ chdir APP_ROOT do
   system 'ruby bin/rake log:clear tmp:clear'
 
   puts "\n== Restarting application server =="
-  touch 'tmp/restart.txt'
+  system 'ruby bin/rake restart'
 end

railties/lib/rails/tasks/restart.rake

 desc "Restart app by touching tmp/restart.txt"
 task :restart do
+  FileUtils.mkdir_p('tmp')
   FileUtils.touch('tmp/restart.txt')
 end

railties/test/application/rake/restart_test.rb

@@ -13,12 +13,12 @@ def setup
       def teardown
         teardown_app
       end
-      
+
       test 'rake restart touches tmp/restart.txt' do
         Dir.chdir(app_path) do
           `rake restart`
           assert File.exist?("tmp/restart.txt")
-          
+
           prev_mtime = File.mtime("tmp/restart.txt")
           sleep(1)
           `rake restart`
@@ -26,6 +26,14 @@ def teardown
           assert_not_equal prev_mtime, curr_mtime
         end
       end
+
+      test 'rake restart should work even if tmp folder does not exist' do
+        Dir.chdir(app_path) do
+          FileUtils.remove_dir('tmp')
+          `rake restart`
+          assert File.exist?('tmp/restart.txt')
+        end
+      end
     end
   end
 end