Redmine 2.3-stable: Append project identifier into mail header 'List-ID'

gistfile1.diff

diff --git a/app/models/mailer.rb b/app/models/mailer.rb
index c12195a..9819776 100644
--- a/app/models/mailer.rb
+++ b/app/models/mailer.rb
@@ -388,6 +388,31 @@ class Mailer < ActionMailer::Base
             'From' => Setting.mail_from,
             'List-Id' => "<#{Setting.mail_from.to_s.gsub('@', '.')}>"

+    # set List-ID
+    if @issue
+        project_id = @issue.project.identifier
+    end
+    if @document
+        project_id = @document.project.identifier
+    end
+    if @attachments
+        project_id = @attachments.first.container.project.identifier
+    end
+    if @news
+        project_id = @news.project.identifier
+    end
+    if @message
+        project_id = @message.project.identifier
+    end
+    if @wiki_content
+        project_id = @wiki_content.project.identifier
+    end
+    if project_id
+      headers 'List-ID' => "#{Setting.host_name}/#{project_id}"
+    else
+      headers 'List-ID' => "<#{Setting.mail_from.to_s.gsub('@', '.')}>"
+    end
+
     # Removes the author from the recipients and cc
     # if he doesn't want to receive notifications about what he does
     if @author && @author.logged? && @author.pref.no_self_notified