Merge branch 'jc/abort-ll-merge-with-a-signal' into next

When the external merge driver is killed by a signal, its output
should not be trusted as a resolution with conflicts that is
proposed by the driver, but the code did.

* jc/abort-ll-merge-with-a-signal:
  t6406: skip "external merge driver getting killed by a signal" test on Windows

t/t6406-merge-attr.sh

@@ -168,7 +168,7 @@ test_expect_success 'custom merge backend' '
 	rm -f $o $a $b
 '
 
-test_expect_success 'custom merge driver that is killed with a signal' '
+test_expect_success !WINDOWS 'custom merge driver that is killed with a signal' '
 	test_when_finished "rm -f output please-abort" &&
 
 	git reset --hard anchor &&