Merge branch 'mm/config-xdg'

Finishing touches to the XDG support (new feature for 1.7.12) and
tests.

* mm/config-xdg:
t1306: check that XDG_CONFIG_HOME works
ignore: make sure we have an xdg path before using it
attr: make sure we have an xdg path before using it
test-lib.sh: unset XDG_CONFIG_HOME

diff --cc dir.c
Simple merge

diff --cc t/test-lib.sh
Simple merge