Merge branch 'jk/no-looking-at-dotgit-outside-repo-final'

This is the endgame of the topic to avoid blindly falling back to ".git" when the setup sequence said we are _not_ in Git repository. A corner case that happens to work right now may be broken by a call to die("BUG"). * jk/no-looking-at-dotgit-outside-repo-final: setup_git_env: avoid blind fall-back to ".git"