add test case for submodule depth parameter

Signed-off-by: Liam Beguin <liambeguin@gmail.com>

Author: liambeguin

git/test/test_submodule.py

@@ -936,3 +936,11 @@ class Repo(object):
         relative_path = Submodule._to_relative_path(super_repo, submodule_path)
         msg = '_to_relative_path should be "submodule_path" but was "%s"' % relative_path
         assert relative_path == 'submodule_path', msg
+
+    @with_rw_directory
+    def test_depth(self, rwdir):
+        parent = git.Repo.init(osp.join(rwdir, 'test_depth'))
+        sm_name = 'mymodules/myname'
+        sm_depth = 1
+        sm = parent.create_submodule(sm_name, sm_name, url=self._small_repo_url(), depth=sm_depth)
+        assert len(list(sm.module().iter_commits())) == sm_depth