Fix Submodule.open() if parent repo is instance of Repository subclass

Author: jorio

pygit2/repository.py

@@ -1548,6 +1548,6 @@ def _from_c(cls, ptr, owned):
         cptr = ffi.new('git_repository **')
         cptr[0] = ptr
         repo = cls.__new__(cls)
-        super(cls, repo)._from_c(bytes(ffi.buffer(cptr)[:]), owned)
+        BaseRepository._from_c(repo, bytes(ffi.buffer(cptr)[:]), owned)
         repo._common_init()
         return repo

test/test_submodule.py

@@ -91,6 +91,20 @@ def test_submodule_open(repo):
     assert r.head.target == SUBM_HEAD_SHA
 
 
+@utils.requires_network
+def test_submodule_open_from_repository_subclass(repo):
+    class CustomRepoClass(pygit2.Repository):
+        pass
+
+    custom_repo = CustomRepoClass(repo.workdir)
+    s = custom_repo.submodules[SUBM_PATH]
+    custom_repo.submodules.init()
+    custom_repo.submodules.update()
+    r = s.open()
+    assert isinstance(r, CustomRepoClass)
+    assert r.head.target == SUBM_HEAD_SHA
+
+
 def test_name(repo):
     s = repo.submodules[SUBM_PATH]
     assert SUBM_NAME == s.name