Merge branch 'jn/maint-setup-fix' (early part) into jn/paginate-fix

Merge branch 'jn/maint-setup-fix' (early part) into jn/paginate-fix

* 'jn/maint-setup-fix' (early part):
  Revert "rehabilitate 'git index-pack' inside the object store"
  setup: do not forget working dir from subdir of gitdir
  t4111 (apply): refresh index before applying patches to it
  setup: split off get_device_or_die helper
  setup: split off a function to handle hitting ceiling in repo search
  setup: split off code to handle stumbling upon a repository
  setup: split off a function to checks working dir for .git file
  setup: split off $GIT_DIR-set case from setup_git_directory_gently
  tests: try git apply from subdir of toplevel
  t1501 (rev-parse): clarify