Allow multiple branches to be protected

Original patch by @moas
diff --git a/tests/no_commit_to_branch_test.py b/tests/no_commit_to_branch_test.py
index 7e39256..c275bf7 100644
--- a/tests/no_commit_to_branch_test.py
+++ b/tests/no_commit_to_branch_test.py
@@ -1,6 +1,8 @@
 from __future__ import absolute_import
 from __future__ import unicode_literals
 
+import pytest
+
 from pre_commit_hooks.no_commit_to_branch import is_on_branch
 from pre_commit_hooks.no_commit_to_branch import main
 from pre_commit_hooks.util import cmd_output
@@ -9,24 +11,24 @@
 def test_other_branch(temp_git_dir):
     with temp_git_dir.as_cwd():
         cmd_output('git', 'checkout', '-b', 'anotherbranch')
-        assert is_on_branch('master') is False
+        assert is_on_branch(('master',)) is False
 
 
 def test_multi_branch(temp_git_dir):
     with temp_git_dir.as_cwd():
         cmd_output('git', 'checkout', '-b', 'another/branch')
-        assert is_on_branch('master') is False
+        assert is_on_branch(('master',)) is False
 
 
 def test_multi_branch_fail(temp_git_dir):
     with temp_git_dir.as_cwd():
         cmd_output('git', 'checkout', '-b', 'another/branch')
-        assert is_on_branch('another/branch') is True
+        assert is_on_branch(('another/branch',)) is True
 
 
 def test_master_branch(temp_git_dir):
     with temp_git_dir.as_cwd():
-        assert is_on_branch('master') is True
+        assert is_on_branch(('master',)) is True
 
 
 def test_main_branch_call(temp_git_dir):
@@ -35,6 +37,13 @@
         assert main(('--branch', 'other')) == 1
 
 
+@pytest.mark.parametrize('branch_name', ('b1', 'b2'))
+def test_forbid_multiple_branches(temp_git_dir, branch_name):
+    with temp_git_dir.as_cwd():
+        cmd_output('git', 'checkout', '-b', branch_name)
+        assert main(('--branch', 'b1', '--branch', 'b2'))
+
+
 def test_main_default_call(temp_git_dir):
     with temp_git_dir.as_cwd():
         cmd_output('git', 'checkout', '-b', 'anotherbranch')