Merge branch 'nd/setup' into next

Merge branch 'nd/setup' into next

* nd/setup: (46 commits)
  git.txt: correct where --work-tree path is relative to
  Revert "Documentation: always respect core.worktree if set"
  t0001: test git init when run via an alias
  Remove all logic from get_git_work_tree()
  setup: rework setup_explicit_git_dir()
  setup: clean up setup_discovered_git_dir()
  t1020-subdirectory: test alias expansion in a subdirectory
  setup: clean up setup_bare_git_dir()
  setup: limit get_git_work_tree()'s to explicit setup case only
  Use git_config_early() instead of git_config() during repo setup
  Add git_config_early()
  git-rev-parse.txt: clarify --git-dir
  t1510: setup case #31
  t1510: setup case #30
  t1510: setup case #29
  t1510: setup case #28
  t1510: setup case #27
  t1510: setup case #26
  t1510: setup case #25
  t1510: setup case #24
  ...