Merge branch 'dl/credential-cache-socket-in-xdg-cache'

The default location "~/.git-credential-cache/socket" for the socket used to communicate with the credential-cache daemon has been moved to "~/.cache/git/credential/socket". * dl/credential-cache-socket-in-xdg-cache: credential-cache: add tests for XDG functionality credential-cache: use XDG_CACHE_HOME for socket path.c: add xdg_cache_home