!!! WIP !!! submodule: gitmodules_config() checks for modified unstaged .gitmodules

Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>
!!! WIP !!! fixup! Teach mv to update the path entry in .gitmodules for moved submodules

Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>