remove trailing whitespace from email bodies

lib/gitlab/email/reply_parser.rb

@@ -15,6 +15,9 @@ module Gitlab
 
         body = EmailReplyTrimmer.trim(body)
 
+        # [jneen] not using /\s+$/ here because that deletes empty lines
+        body = body.gsub(/[ \t]$/, '')
+
         # TODO [jneen]: do we want to allow empty-quoting? (replies only containing a blockquote)
         # EmailReplyTrimmer allows this as a special case, so we detect it manually here.
         return "" if body.lines.all? { |l| l.strip.empty? || l.start_with?('>') }