Merge branch 'jk/rev-parse-local-env-vars' into maint

The "--local-env-vars" and "--resolve-git-dir" options of "git rev-parse" failed to work outside a repository when the command's option parsing was rewritten in 1.8.5 era. * jk/rev-parse-local-env-vars: rev-parse: let some options run outside repository t1515: add tests for rev-parse out-of-repo helpers