How does Xcode work with Git to change the start command and check?

Since Xcode version 4.4.1 does not have the function of branching or checking the old version, is it possible to do this in bash

git checkout in-app-purchase-to-be-added

or

git checkout HEAD^2

because all the source code ( .m, .h), .xiband the project files, image resources will change instantly, so that this will not cause strange behavior in Xcode? Right now, I always leave Xcode, switch the branch, and restart Xcode, but there may be a faster way.