This is what source control is for. You switch to the branch and hack on it. In the rare case you need different versions of dependencies, you use a tool like

This is what source control is for. You switch to the branch and hack on it. In the rare case you need different versions of dependencies, you use a tool like godep (but if you have to resort to that, you're doing something wrong, your dependencies should have stable APIs). Don't use multiple spots on your hard drive for code in source control. Use source control for what it's made for.