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

diff --cc cache.h
Simple merge