explains why the file update checker ignores mtimes in the future, plus a...

explains why the file update checker ignores mtimes in the future, plus a little refactor for the same price

activesupport/lib/active_support/file_update_checker.rb

@@ -101,9 +101,19 @@ def watched
     end
 
     def updated_at(paths)
+      @updated_at || max_mtime(paths) || Time.at(0)
+    end
+
+    # This method returns the maximum mtime of the files in +paths+, or +nil+
+    # if the array is empty.
+    #
+    # Files with a mtime in the future are ignored. Such abnormal situation
+    # can happen for example if the user changes the clock by hand. It is
+    # healthy to consider this edge case because with mtimes in the future
+    # reloading is not triggered.
+    def max_mtime(paths)
       time_now = Time.now
-      @updated_at || paths.map { |path| File.mtime(path) }.
-        reject { |time| time > time_now }.max || Time.at(0)
+      paths.map {|path| File.mtime(path)}.reject {|mtime| time_now < mtime}.max
     end
 
     def compile_glob(hash)