3 Tracked fields is generic logging system for the changes applied to some fields in open chatter.
4 - In the definition of a fields. you have to simply add tracked=True.
5 - When changing one of the fields having tracked=True on saved automatically write a log in openchatter for the changes in fields.
9 - You have to add tracked=True in field defination as following.
10 - ``'stage_id': fields.many2one('project.task.type', 'Stage',tracked=True),``
11 - For developed this feature we override write method of mail_thread.
12 - And make one mako template which shows old field and updated field.
16 - After changing field follower can show log of tracked field in open chatter as followed.
18 - Stage: Analysis -> Specification