Hi,
A direct integration with Cognos portal is only possible with paid tools like Motio CI, Cognos Toolkit etc. Or you have to build some kind of extension to integrate Git or any other source control by writing your own API method calls and calling them using javascript from the extension. The other way is to manually copy the specification to a file and using source control to track the file check in / check outs.
If you are just looking for audit information, you can find that from Audit Package / Reports that come with cognos samples. There is a report that shows actions on objects like Update, Delete, Add, Query etc.
Regards
Kiran
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Kiran Passumarthi
www.linkedin.com/in/kiranpassumarthi------------------------------