Push to github with --force.

MultiPart: 2/2
Change-Id: Iaba7d1a15c92f2615a1640f63a38863dbd3d767c
diff --git a/jiri-test/internal/test/github.go b/jiri-test/internal/test/github.go
index 4f38077..6747212 100644
--- a/jiri-test/internal/test/github.go
+++ b/jiri-test/internal/test/github.go
@@ -281,5 +281,5 @@
 func push(jirix *jiri.X, mirror Mirror, projects string) error {
 	dirname := filepath.Join(projects, mirror.name)
 	opts := gitutil.RootDirOpt(dirname)
-	return gitutil.New(jirix.NewSeq(), opts).Push(mirror.github, "master")
+	return gitutil.New(jirix.NewSeq(), opts).Push(mirror.github, "master", gitutil.ForceOpt(true))
 }