Merge branch 'ps/setup-drop-global-state'

Merge branch 'ps/setup-drop-global-state'

The refactoring of 'setup.c' has been continued to drop remaining
global state (`git_work_tree_cfg`, `is_bare_repository_cfg`), updating
`is_bare_repository()` to no longer implicitly rely on
`the_repository`.

* ps/setup-drop-global-state:
  treewide: drop USE_THE_REPOSITORY_VARIABLE
  environment: stop using `the_repository` in `is_bare_repository()`
  environment: split up concerns of `is_bare_repository_cfg`
  builtin/init: stop modifying `is_bare_repository_cfg`
  setup: remove global `git_work_tree_cfg` variable
  builtin/init: simplify logic to configure worktree
  builtin/init: stop modifying global `git_work_tree_cfg` variable