Merge branch 'pw/diff-no-index-from-named-pipes' into next

Test updates.

* pw/diff-no-index-from-named-pipes:
  t4053: avoid writing to unopened pipe
  t4053: avoid race when killing background processes

t/t4053-diff-no-index.sh

@@ -232,10 +232,6 @@ test_expect_success 'diff --no-index refuses to diff stdin and a directory' '
 test_expect_success PIPE 'diff --no-index refuses to diff a named pipe and a directory' '
 	test_when_finished "rm -f pipe" &&
 	mkfifo pipe &&
-	{
-		(>pipe) &
-	} &&
-	test_when_finished "kill $!" &&
 	test_must_fail git diff --no-index -- pipe a 2>err &&
 	grep "fatal: cannot compare a named pipe to a directory" err
 '
@@ -248,11 +244,11 @@ test_expect_success PIPE,SYMLINKS 'diff --no-index reads from pipes' '
 	{
 		(test_write_lines a b c >old) &
 	} &&
-	test_when_finished "! kill $!" &&
+	test_when_finished "kill $! || :" &&
 	{
 		(test_write_lines a x c >new) &
 	} &&
-	test_when_finished "! kill $!" &&
+	test_when_finished "kill $! || :" &&
 
 	cat >expect <<-EOF &&
 	diff --git a/old b/new-link