Merge branch 'jc/safe-implicit-bare'

Users with safe.bareRepository=explicit can still work from within
$GIT_DIR of a seconary worktree (which resides at .git/worktrees/$name/)
of the primary worktree without explicitly specifying the $GIT_DIR
environment variable or the --git-dir=<path> option.

* jc/safe-implicit-bare:
  setup: notice more types of implicit bare repositories

diff --cc setup.c
Simple merge