Merge branch 'pt/xdg-config-path' into maint

Code clean-up for xdg configuration path support.

* pt/xdg-config-path:
  path.c: remove home_config_paths()
  git-config: replace use of home_config_paths()
  git-commit: replace use of home_config_paths()
  credential-store.c: replace home_config_paths() with xdg_config_home()
  dir.c: replace home_config_paths() with xdg_config_home()
  attr.c: replace home_config_paths() with xdg_config_home()
  path.c: implement xdg_config_home()
  t0302: "unreadable" test needs POSIXPERM
  t0302: test credential-store support for XDG_CONFIG_HOME
  git-credential-store: support XDG_CONFIG_HOME
  git-credential-store: support multiple credential files

diff --cc attr.c
Simple merge

diff --cc builtin/commit.c
Simple merge

diff --cc builtin/config.c
Simple merge

diff --cc cache.h
Simple merge

diff --cc config.c
Simple merge

diff --cc credential-store.c
Simple merge

diff --cc dir.c
Simple merge

diff --cc path.c
Simple merge