From: Eric Wong <normalperson@...>
Date: 2015-01-23T23:47:07+00:00
Subject: [ruby-core:67775] Re: Preventing Redundant Email Messages

SHIBATA Hiroshi <shibata.hiroshi@gmail.com> wrote:
> It's a bug of plugin for ruby-core ML integration.
> 
>  * https://github.com/ruby/redmine_mailing_list_integration

I don't know redmine internals either, but taking a quick look,
I think it is from commit 059c6c4fcaa94f3675eda17bfe2f05401b84e70b

Before: nil => true
 After: nil => false

The date also matches around when I started noticing the duplicates.

commit 059c6c4fcaa94f3675eda17bfe2f05401b84e70b
Author: SHIBATA Hiroshi <shibata.hiroshi@gmail.com>
Date:   Thu Jan 16 05:40:36 2014 +0900

    style

:100644 100644 6507432... 68737e1... M	app/models/based_on_mail.rb
:100644 100644 53c61a9... e65ad42... M	lib/redmine_mailing_list_integration/redmine_ext/issue.rb

diff --git a/app/models/based_on_mail.rb b/app/models/based_on_mail.rb
index 6507432..68737e1 100644
--- a/app/models/based_on_mail.rb
+++ b/app/models/based_on_mail.rb
@@ -1,10 +1,6 @@
 module BasedOnMail
   def originates_from_mail?
-    if @originates_from_mail.nil?
-      @originates_from_mail = true
-    else
-      @originates_from_mail
-    end
+    !!@originates_from_mail
   end
   attr_writer :originates_from_mail
 end