Merge branch 'kh/maintenance-use-xdg-when-it-should'

When $HOME/.gitignore is missing but XDG config file available, we should write into the latter, not former. "git gc" and "git maintenance" wrote into a wrong "global config" file, which have been corrected. * kh/maintenance-use-xdg-when-it-should: maintenance: use XDG config if it exists config: factor out global config file retrieval config: rename global config function config: format newlines