Merge branch 'sb/submodule-recursive-absorb'

When a submodule "A", which has another submodule "B" nested within
it, is "absorbed" into the top-level superproject, the inner
submodule "B" used to be left in a strange state.  The logic to
adjust the .git pointers in these submodules has been corrected.

* sb/submodule-recursive-absorb:
  submodule absorbing: fix worktree/gitdir pointers recursively for non-moves
  cache.h: expose the dying procedure for reading gitlinks
  setup: add gentle version of resolve_git_dir

diff --cc cache.h
Simple merge