Merge branch 'ps/setup-split-discovery-and-setup'

The repository discovery and repository configuration phases, which were previously intertwined in 'setup.c', have been split. Repository discovery has been updated to populate a 'struct repo_discovery' without modifying the repository state, which is then taken by repository configuration to initialize the repository, paving the way for clean unification of repository configuration. * ps/setup-split-discovery-and-setup: setup: mark `set_git_work_tree()` as file-local setup: pass worktree to `init_db()` setup: drop redundant configuration of `startup_info->have_repository` setup: make repository discovery self-contained setup: propagate prefix via repository discovery setup: drop static `cwd` variable setup: move prefix into repository setup: embed repository format in discovery setup: introduce explicit repository discovery setup: split up concerns of `setup_git_env_internal()` setup: unify setup of shallow file setup: mark bogus worktree in `apply_repository_format()` setup: rename `check_repository_format_gently()`