[PATCH] test: fix for TEST_OUTPUT_DIRECTORY

The test_atexit unit test relies on the specific location of the generated files.

When TEST_OUTPUT_DIRECTORY is unset, _run_sub_test_lib_test_common sets it to pwd, which is two levels under the pwd of the parent unit test, and the parent can find the generated files just fine.

But when TEST_OUTPUT_DIRECTORY is set, it's stored in GIT-BUILD-OPTIONS, and even though _run_sub_test_lib_test_common correctly overrides it, when the child script is run, it sources GIT-BUILD-OPTIONS, and TEST_OUTPUT_DIRECTORY is overridden.

Effectively both the parent and child scripts output to the same directory.

  make TEST_OUTPUT_DIRECTORY=/tmp/foobar GIT-BUILD-OPTIONS &&
  make -C t t0000-basic.sh

We could simply revert 2d14e13c56 (test output: respect $TEST_OUTPUT_DIRECTORY, 2013-04-29), but presumably it was done for some reason.

On the other hand we could follow the alternate path suggested in 6883047071 (t0000: set TEST_OUTPUT_DIRECTORY for sub-tests, 2013-12-28): pass the --root parameter to the child scripts.

The alternate solution works, so let's do that instead.

Presumably this was broken since 900721e15c (test-lib: introduce 'test_atexit', 2019-03-13).

Cc: John Keeping <john@keeping.me.uk>
Cc: Jeff King <peff@peff.net>
Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
---
 t/t0000-basic.sh | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)