tests: let --immediate and --write-junit-xml play well together

When the `--immediate` option is in effect, any test failure will
immediately exit the test script. Together with `--write-junit-xml`, we
will want the JUnit-style `.xml` file to be finalized (and not leave the
XML incomplete). Let's make it so.

This comes in particularly handy when trying to debug via Azure
Pipelines, where the JUnit-style XML is consumed to present the test
results in an informative and helpful way.

While at it, also handle the `error()` code path.

The only remaining code path that sets `GIT_EXIT_OK` happens whenever
the trash directory could not be set up, i.e. long before the JUnit XML
was written, therefore we should _not_ try to finalize that XML in that
case.

It is tempting to change the `immediate` code path to just hand off to
`error`, simplifying the code in the process. That would, however,
result in a change of behavior (an additional error message) in the test
suite, which is outside of the purview of the current patch series: its
goal is to allow building Git with Visual Studio and testing it with a
portable version of Git for Windows.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -567,6 +567,7 @@ export TERM
 
 error () {
 	say_color error "error: $*"
+	finalize_junit_xml
 	GIT_EXIT_OK=t
 	exit 1
 }
@@ -695,7 +696,7 @@ test_failure_ () {
 	say_color error "not ok $test_count - $1"
 	shift
 	printf '%s\n' "$*" | sed -e 's/^/#	/'
-	test "$immediate" = "" || { GIT_EXIT_OK=t; exit 1; }
+	test "$immediate" = "" || { finalize_junit_xml; GIT_EXIT_OK=t; exit 1; }
 }
 
 test_known_broken_ok_ () {
@@ -1063,6 +1064,25 @@ write_junit_xml_testcase () {
 	junit_have_testcase=t
 }
 
+finalize_junit_xml () {
+	if test -n "$write_junit_xml" && test -n "$junit_xml_path"
+	then
+		test -n "$junit_have_testcase" || {
+			junit_start=$(test-tool date getnanos)
+			write_junit_xml_testcase "all tests skipped"
+		}
+
+		# adjust the overall time
+		junit_time=$(test-tool date getnanos $junit_suite_start)
+		sed "s/<testsuite [^>]*/& time=\"$junit_time\"/" \
+			<"$junit_xml_path" >"$junit_xml_path.new"
+		mv "$junit_xml_path.new" "$junit_xml_path"
+
+		write_junit_xml "  </testsuite>" "</testsuites>"
+		write_junit_xml=
+	fi
+}
+
 test_atexit_cleanup=:
 test_atexit_handler () {
 	# In a succeeding test script 'test_atexit_handler' is invoked
@@ -1085,21 +1105,7 @@ test_done () {
 	# removed, so the commands can access pidfiles and socket files.
 	test_atexit_handler
 
-	if test -n "$write_junit_xml" && test -n "$junit_xml_path"
-	then
-		test -n "$junit_have_testcase" || {
-			junit_start=$(test-tool date getnanos)
-			write_junit_xml_testcase "all tests skipped"
-		}
-
-		# adjust the overall time
-		junit_time=$(test-tool date getnanos $junit_suite_start)
-		sed "s/<testsuite [^>]*/& time=\"$junit_time\"/" \
-			<"$junit_xml_path" >"$junit_xml_path.new"
-		mv "$junit_xml_path.new" "$junit_xml_path"
-
-		write_junit_xml "  </testsuite>" "</testsuites>"
-	fi
+	finalize_junit_xml
 
 	if test -z "$HARNESS_ACTIVE"
 	then