repo: add --version support to the launcher

We can get version info when in a checkout, but it'd be helpful
to show that info at all times.

Change-Id: Ieeb44a503c9d7d8c487db4810bdcf3d5f6656c82
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254712
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

tests/test_wrapper.py

@@ -26,6 +26,14 @@ from pyversion import is_python3
 import wrapper
 
 
+if is_python3():
+  from unittest import mock
+  from io import StringIO
+else:
+  import mock
+  from StringIO import StringIO
+
+
 def fixture(*paths):
   """Return a path relative to tests/fixtures.
   """
@@ -48,6 +56,16 @@ class RepoWrapperUnitTest(RepoWrapperTestCase):
   """Tests helper functions in the repo wrapper
   """
 
+  def test_version(self):
+    """Make sure _Version works."""
+    with self.assertRaises(SystemExit) as e:
+      with mock.patch('sys.stdout', new_callable=StringIO) as stdout:
+        with mock.patch('sys.stderr', new_callable=StringIO) as stderr:
+          self.wrapper._Version()
+    self.assertEqual(0, e.exception.code)
+    self.assertEqual('', stderr.getvalue())
+    self.assertIn('repo launcher version', stdout.getvalue())
+
   def test_get_gitc_manifest_dir_no_gitc(self):
     """
     Test reading a missing gitc config file