Fix upstream.sh presubmit test for git 1.8.3+

tests/test-lib.sh

Index: tests/test-lib.sh
diff --git a/tests/test-lib.sh b/tests/test-lib.sh
index ad078180437b8b16700bd79fb66abab331ebc412..92ec3bbdd4c1457564d83c00d720b3743fc9ea94 100755
--- a/tests/test-lib.sh
+++ b/tests/test-lib.sh
@@ -49,9 +49,10 @@ setup_gitsvn() {
   rm -rf git-svn
   # There appears to be no way to make git-svn completely shut up, so we
   # redirect its output.
-  git svn -q clone -s $REPO_URL git-svn >/dev/null 2>&1
+  git svn --prefix origin/ -q clone -s $REPO_URL git-svn >/dev/null 2>&1
   (
     cd git-svn
+    git remote add origin https://example.com/fake_refspec
     git config user.name 'TestDood'
     git config user.email 'TestDood@example.com'
   )