Merge branch 'sb/submodule-helper-clone-regression-fix' into sb/submodule-init

Merge branch 'sb/submodule-helper-clone-regression-fix' into sb/submodule-init

* sb/submodule-helper-clone-regression-fix:
  submodule--helper, module_clone: catch fprintf failure
  submodule--helper: do not borrow absolute_path() result for too long
  submodule--helper, module_clone: always operate on absolute paths
  submodule--helper clone: create the submodule path just once
  submodule--helper: fix potential NULL-dereference
  recursive submodules: test for relative paths