I just found out by accident that you can easily manage to achieve this:

• fork the project (if you haven‘t done it yet)
• create a pull request for yourself from the selected branch, e.g. from master of head project to master of your fork:
  • base fork: original/project ; base: master ; head fork: your/project ; compare: master
• do NOT merge this pull request
• under the Email section of your Notifications settings enable:
  • Comments on Issues and Pull Requests
  • Pull Request reviews
  • Pull Request pushes

That‘s it. You will receive email notifications about every commit on master branch.