[PATCH v3/GSoC 4/5] test-lib.sh: unset all environment variables defined in xdg base dir spec[1]

[Hui Yiqun <huiyiqun@gmail.com>]

Otherwise, on environments where these variables and set, an assignment
to one of these variables will cause the variable being implicitly exported.

For example:

    $ XDG_RUNTIME_DIR=/run/user/2000 bash
    $ XDG_RUNTIME_DIR=/tmp/whatever # it should not be exported!
    $ bash
    $ echo $XDG_RUNTIME_DIR
    /tmp/whatever # instead of empty

[1] https://specifications.freedesktop.org/basedir-spec
    /basedir-spec-latest.html

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Hui Yiqun <huiyiqun@gmail.com>
---
 t/test-lib.sh | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/t/test-lib.sh b/t/test-lib.sh
index 0b47eb6..60a837a 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -93,7 +93,17 @@ unset VISUAL EMAIL LANGUAGE COLUMNS $("$PERL_PATH" -e '
 	my @vars = grep(/^GIT_/ && !/^GIT_($ok)/o, @env);
 	print join("\n", @vars);
 ')
+# Unset all environment variables defined in xdg base dir spec[1]
+# to make sure that the test are running with a known state.
+#
+# [1] https://specifications.freedesktop.org/basedir-spec
+#     /basedir-spec-latest.html
+unset XDG_DATA_HOME
 unset XDG_CONFIG_HOME
+unset XDG_DATA_DIRS
+unset XDG_CONFIG_DIRS
+unset XDG_CACHE_HOME
+unset XDG_RUNTIME_DIR
 unset GITPERLLIB
 GIT_AUTHOR_EMAIL=author@example.com
 GIT_AUTHOR_NAME='A U Thor'
-- 
2.7.4