In MR !749, the "manual" OpenMesh instance was replaced by a direct fetch from git. While the idea is good and should be the default, we should also offer the alternative of providing the path to the OpenMesh repository manually if the git fetch fails. This could be the case if there is no Internet connection like it is often the case on clusters, or some issues with firewalls etc. Right now, if git fetch fails, there is no means to build waLBerla anymore, even if a local instance of OpenMesh is present. Closely related to issue #271.