Merge branch 'ps/gc-stale-lock-warning' into next

Give a bit of advice/hint message when "git maintenance" stops finding a
lock file left by another instance that still is potentially running.

* ps/gc-stale-lock-warning:
  t7900: fix host-dependent behaviour when testing git-maintenance(1)

Author: gitster

t/t7900-maintenance.sh

@@ -1011,10 +1011,15 @@ test_expect_success 'repacking loose objects is quiet' '
 '
 
 test_expect_success 'maintenance aborts with existing lock file' '
-	test_when_finished "rm -rf repo" &&
+	test_when_finished "rm -rf repo script" &&
+	mkdir script &&
+	write_script script/systemctl <<-\EOF &&
+	true
+	EOF
+
 	git init repo &&
 	: >repo/.git/objects/schedule.lock &&
-	test_must_fail git -C repo maintenance start 2>err &&
+	test_must_fail env PATH="$PWD/script:$PATH" git -C repo maintenance start --scheduler=systemd 2>err &&
 	test_grep "Another scheduled git-maintenance(1) process seems to be running" err
 '