Merge branch 'pb/recurse-submodules-fix'

Fix "git checkout --recurse-submodules" of a nested submodule
hierarchy.

* pb/recurse-submodules-fix:
  t/lib-submodule-update: add test removing nested submodules
  unpack-trees: check for missing submodule directory in merged_entry
  unpack-trees: remove outdated description for verify_clean_submodule
  t/lib-submodule-update: move a test to the right section
  t/lib-submodule-update: remove outdated test description
  t7112: remove mention of KNOWN_FAILURE_SUBMODULE_RECURSIVE_NESTED

diff --cc unpack-trees.c
Simple merge