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"

diff --cc environment.c
Simple merge