t4014-format-patch: do not assume 'test' is available as non-builtin
t4014-format-patch: do not assume 'test' is available as non-builtin

One test case used 'xargs test', which assumes that 'test' is available
as external program. At least on MinGW it is not.

Moreover, 'git format-patch' was invoked in a pipeline, but not as the
last command. Rewrite the test case to catch breakage in 'git format-patch'
as well.

Signed-off-by: Johannes Sixt <fd432345609ae4d58c1aa629cb66ba96d1391622@kdbg.org>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git