--- redmine/lib/redmine/codeset_util.rb 2016-10-10 14:48:13.000000000 +0700
+++ redmine/lib/redmine/codeset_util.rb.n       2017-07-13 15:24:10.791827525 +0700
@@ -1,3 +1,4 @@
+require 'rchardet'

 module Redmine
   module CodesetUtil
@@ -46,6 +47,7 @@
       return str if /\A[\r\n\t\x20-\x7e]*\Z/n.match(str) # for us-ascii
       str.force_encoding('UTF-8')
       encodings = Setting.repositories_encodings.split(',').collect(&:strip)
+      encodings.unshift(CharDet.detect(str)['encoding'])
       encodings.each do |encoding|
         begin
           str.force_encoding(encoding)