Step 1 : Go to Bugs tab. Click changesets. This displays all changesets of a project with link to the github commit.
Step 2 : Click on the commit link. This redirects to github respository and you can find the actual changes done in the source code compared to the previous version of the code.
Step 3 : Click Source link and see the list of files checked into this respository.
Step 4: Click Commit link and you can find the commit history of your project repository.