remote-hg: add test for diverged push

Neither mercurial nor git allows pushing to a remote when it's a
non-fast-forward push. We should be able to detect these errors and
report them properly, as opposed to throwing an exception
stack-trace.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/remote-helpers/test-hg.sh

@@ -318,4 +318,27 @@ test_expect_success 'remote new bookmark' '
 	check_bookmark hgrepo feature-b feature-b
 '
 
+test_expect_failure 'remote push diverged' '
+	test_when_finished "rm -rf gitrepo*" &&
+
+	git clone "hg::hgrepo" gitrepo &&
+
+	(
+	cd hgrepo &&
+	hg checkout default &&
+	echo bump > content &&
+	hg commit -m bump
+	) &&
+
+	(
+	cd gitrepo &&
+	echo diverge > content &&
+	git commit -a -m diverged &&
+	test_expect_code 1 git push 2> error &&
+	grep "^ ! \[rejected\] *master -> master (non-fast-forward)$" error
+	) &&
+
+	check_branch hgrepo default bump
+'
+
 test_done