clone: add test for push on an empty clone.

Commit 55f0566 (get_local_heads(): do not return random pointer if
there is no head, 2009-04-17) fixed a segfault for git push, this
patch adds a test-case to avoid future regressions.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5701-clone-local.sh

@@ -132,4 +132,14 @@ test_expect_success 'clone empty repository' '
 	 test $actual = $expected)
 '
 
+test_expect_success 'clone empty repository, and then push should not segfault.' '
+	cd "$D" &&
+	rm -fr empty/ empty-clone/ &&
+	mkdir empty &&
+	(cd empty && git init) &&
+	git clone empty empty-clone &&
+	cd empty-clone &&
+	test_must_fail git push
+'
+
 test_done