git checkout 12abcd # check that we can build at this stage, make sure that you have all your changes out of tree, just in case: git clean -dfX && cd win32 && gmake test # Create the new branch here, and check it out git branch makefile-update git checkout makefile-update ... apply your changes # check that tests still pass git clean -dfX && cd win32 && gmake test git commit -m "voila" git push github