test-lib: Don't write test-results when HARNESS_ACTIVE

TAP harnesses don't need to read test-results/*, since they keep track
of the number of passing/failing tests internally. Skip the generation
of these files when HARNESS_ACTIVE is set.

It's now possible to run the Git test suite without writing anything
to the t/ directory at all if you use a TAP harness and the --root
switch:

    cd t
    sudo mount -t tmpfs none /tmp/memory -o size=300m
    prove -j9 ./t[0-9]*.sh :: --root=/tmp/memory

The I/O that the ~500 test-results/* files contributed was very
minimal, but I thought this was worth mentioning.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -633,16 +633,19 @@ test_create_repo () {
 
 test_done () {
 	GIT_EXIT_OK=t
-	test_results_dir="$TEST_DIRECTORY/test-results"
-	mkdir -p "$test_results_dir"
-	test_results_path="$test_results_dir/${0%.sh}-$$.counts"
-
-	echo "total $test_count" >> $test_results_path
-	echo "success $test_success" >> $test_results_path
-	echo "fixed $test_fixed" >> $test_results_path
-	echo "broken $test_broken" >> $test_results_path
-	echo "failed $test_failure" >> $test_results_path
-	echo "" >> $test_results_path
+
+	if test -z "$HARNESS_ACTIVE"; then
+		test_results_dir="$TEST_DIRECTORY/test-results"
+		mkdir -p "$test_results_dir"
+		test_results_path="$test_results_dir/${0%.sh}-$$.counts"
+
+		echo "total $test_count" >> $test_results_path
+		echo "success $test_success" >> $test_results_path
+		echo "fixed $test_fixed" >> $test_results_path
+		echo "broken $test_broken" >> $test_results_path
+		echo "failed $test_failure" >> $test_results_path
+		echo "" >> $test_results_path
+	fi
 
 	if test "$test_fixed" != 0
 	then