If you are maintaining an application you may need to return to an earlier branch to test. For instance, the bug you're fixing may have been around, but unreported, for a long time. You'll want to find when the bug was introduced to track down the code that introduced it. (Refer to git bisect in the Finding bugs recipe in this chapter.)
When you add new features, you should create a new branch to identify your changes. The project maintainer can then merge the new branch into the master branch after the new code is tested and validated. You can change and create new branches with the git's checkout subcommand.
