Modman is a nice little module manager for Magento. If you work on any Magento projects then I’d suggest you get familiar with it, as it’ll save you loads of time when creating/installing your own Magento extensions. The Modman has a Wiki for it’s documentation.
When installing a Magento extension under git through modman, you can specify a branch like so:
modman clone https://yourgit.repo -b 'branch-name'
Make sure you include the ‘ around the branch name or you will get errors.