setup: mark bogus worktree in `apply_repository_format()`

setup: mark bogus worktree in `apply_repository_format()`

When a repository is configured to have both "core.worktree" and
"core.bare" we emit a warning and mark the worktree configuration as
bogus so that the next call to `setup_work_tree()` will cause us to die.
This allows us to still use the misconfigured repository, at least as
long as we don't try to use its worktree.

This condition is handled in `setup_explicit_git_dir()`. In a subsequent
commit we'll refactor this function so that it doesn't receive a repo as
input anymore though, and consequently we cannot set the "bogus" bit
anymore.

Move the logic into `apply_repository_format()` instead to prepare for
this. While at it, fix up formatting a bit.

Note that this change requires us to also explicitly unset the value of
"core.worktree" in case we have the "GIT_WORK_TREE" environment variable
set. This is because the environment variable overrides the repository's
configuration, and we don't want to warn or die in case the work tree
has been configured explicitly regardless of whether or not "core.bare"
is set.

Signed-off-by: Patrick Steinhardt <redacted>
Signed-off-by: Junio C Hamano <redacted>