Keeping the old relative URLs is a nightmare during forking. When someone forks a repo only the specific repo is cloned and not the submodules. Therefor when he tries to clone it recursively including all submodules to his local drive, git tries to access the submodules based on the relative path which now, because of the forking, points to the contributors's git account instead of enyo's and the cloning crashes since the submodules can not be found.