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

A partial rewrite of "git submodule" in the 2.7 timeframe changed the way the gitdir: pointer in the submodules point at the real repository location to use absolute paths by accident. This has been corrected. * 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