Reset reconstructed dependency fixture branches

GitPython tests used the former submodules as clonable gitdb and smmap
repositories. Reconstructing those fixtures from a shared clone of the merged
history initially inherited GitPython's master branch and tag namespace,
causing branch and tag creation collisions.

Force the fixture branch and historical smmap tag to the imported source tips
so the reconstructed repositories have the same refs the existing tests
expect.

Author: codex

test/lib/helper.py

@@ -408,7 +408,7 @@ def setUpClass(cls):
         }.items():
             path = osp.join(cls._dependency_repo_root, name)
             repo = cls.rorepo.clone(path, shared=True, no_checkout=True)
-            repo.create_head("master", repo.commit(rev)).checkout()
+            repo.create_head("master", repo.commit(rev), force=True).checkout()
             if name == "smmap":
                 repo.create_tag("v0.8.1", ref="master~10", message="Test fixture tag")
             repo.close()