update helper to active_support 4.2.4

Author: MichaelSp

lib/filewatch/helper.rb

@@ -1,5 +1,5 @@
-# code downloaded from Ruby on Rails 4.2.1
-# https://raw.githubusercontent.com/rails/rails/v4.2.1/activesupport/lib/active_support/core_ext/file/atomic.rb
+# code downloaded from Ruby on Rails 4.2.4
+# https://raw.githubusercontent.com/rails/rails/v4.2.4/activesupport/lib/active_support/core_ext/file/atomic.rb
 require 'fileutils'
 
 class File
@@ -16,7 +16,14 @@ class File
   #   File.atomic_write('/data/something.important', '/data/tmp') do |file|
   #     file.write('hello')
   #   end
-  def self.atomic_write(file_name)
+  def self.atomic_write(file_name, temp_dir = Dir.tmpdir)
+    require 'tempfile' unless defined?(Tempfile)
+    require 'fileutils' unless defined?(FileUtils)
+
+    temp_file = Tempfile.new(basename(file_name), temp_dir)
+    temp_file.binmode
+    yield temp_file
+    temp_file.close
 
     if File.exist?(file_name)
       # Get original file permissions
@@ -27,42 +34,35 @@ def self.atomic_write(file_name)
       old_stat = probe_stat_in(dirname(file_name))
     end
 
-    mode = old_stat ? old_stat.mode : nil
-
-    # Create temporary file with identical permissions
-    temp_file = File.new(rand_filename(file_name), "w", mode)
-    temp_file.binmode
-    return_val = yield temp_file
-    temp_file.close
-
     # Overwrite original file with temp file
-    File.rename(temp_file.path, file_name)
+    FileUtils.mv(temp_file.path, file_name)
 
-    # Unable to get permissions of the original file => return
-    return return_val if old_stat.nil?
-
-    # Set correct uid/gid on new file
-    chown(old_stat.uid, old_stat.gid, file_name) if old_stat
-
-    return_val
+    # Set correct permissions on new file
+    begin
+      chown(old_stat.uid, old_stat.gid, file_name)
+      # This operation will affect filesystem ACL's
+      chmod(old_stat.mode, file_name)
+    rescue Errno::EPERM, Errno::EACCES
+      # Changing file ownership failed, moving on.
+    end
   end
 
   # Private utility method.
   def self.probe_stat_in(dir) #:nodoc:
-    basename = rand_filename(".permissions_check")
+    basename = [
+      '.permissions_check',
+      Thread.current.object_id,
+      Process.pid,
+      rand(1000000)
+    ].join('.')
+
     file_name = join(dir, basename)
     FileUtils.touch(file_name)
     stat(file_name)
-  rescue
-    # ...
   ensure
-    FileUtils.rm_f(file_name) if File.exist?(file_name)
+    FileUtils.rm_f(file_name) if file_name
   end
-
-  def self.rand_filename(prefix)
-    [ prefix, Thread.current.object_id, Process.pid, rand(1000000) ].join('.')
-  end
-
+  
   def self.device?(file_name)
     chardev?(file_name) || blockdev?(file_name)
   end