[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 <redacted>
Cc: Jeff King <redacted>
Cc: Johannes Schindelin <redacted>
Signed-off-by: Felipe Contreras <redacted>
---
 t/t0000-basic.sh | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
index 705d62cc27..16b70ef940 100755
--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh

@@ -93,14 +93,12 @@ _run_sub_test_lib_test_common () {
 		EOF
 		cat >>"$name.sh" &&
 		export TEST_DIRECTORY &&
-		TEST_OUTPUT_DIRECTORY=$(pwd) &&
-		export TEST_OUTPUT_DIRECTORY &&
 		sane_unset GIT_TEST_FAIL_PREREQS &&
 		if test -z "$neg"
 		then
-			./"$name.sh" "$@" >out 2>err
+			./"$name.sh" --root="$(pwd)" "$@" >out 2>err
 		else
-			! ./"$name.sh" "$@" >out 2>err
+			! ./"$name.sh" --root="$(pwd)" "$@" >out 2>err
 		fi
 	)
 }

-- 
2.32.0.2.g41be0a4e50