credentials: memory safety

The docs say to use tp_free() to free the memory, and even though we use
PyObject_Del() everywhere else, using this in the credentials does cause
issues.

src/credentials.c

@@ -72,7 +72,7 @@ CredUsernamePassword_dealloc(CredUsernamePassword *self)
     free(self->username);
     free(self->password);
 
-    PyObject_Del(self);
+    Py_TYPE(self)->tp_free(self);
 }
 
 PyMemberDef CredUsernamePassword_members[] = {
@@ -169,7 +169,7 @@ CredSshKey_dealloc(CredSshKey *self)
     free(self->privkey);
     free(self->passphrase);
 
-    PyObject_Del(self);
+    Py_TYPE(self)->tp_free(self);
 }
 
 PyMemberDef CredSshKey_members[] = {

src/pygit2.c

@@ -154,7 +154,7 @@ clone_repository(PyObject *self, PyObject *args) {
     const char *path;
     unsigned int bare, ignore_cert_errors;
     const char *remote_name, *checkout_branch;
-    PyObject *credentials;
+    PyObject *credentials = NULL;
     int err;
     git_clone_options opts = GIT_CLONE_OPTIONS_INIT;
 
@@ -167,8 +167,10 @@ clone_repository(PyObject *self, PyObject *args) {
     opts.remote_name = remote_name;
     opts.checkout_branch = checkout_branch;
 
-    opts.remote_callbacks.credentials = credentials_cb;
-    opts.remote_callbacks.payload = credentials;
+    if (credentials != Py_None) {
+	    opts.remote_callbacks.credentials = credentials_cb;
+	    opts.remote_callbacks.payload = credentials;
+    }
 
     err = git_clone(&repo, url, path, &opts);
     if (err < 0)

src/utils.c

@@ -202,9 +202,9 @@ int
 callable_to_credentials(git_cred **out, const char *url, const char *username_from_url, unsigned int allowed_types, PyObject *credentials)
 {
     int err;
-    PyObject *py_cred, *arglist;
+    PyObject *py_cred = NULL, *arglist = NULL;
 
-    if (credentials == NULL)
+    if (credentials == NULL || credentials == Py_None)
         return 0;
 
     if (!PyCallable_Check(credentials)) {

test/test_repository.py

@@ -461,6 +461,13 @@ class CloneRepositoryTest(utils.NoRepoTestCase):
         self.assertFalse(repo.is_empty)
         self.assertEqual(repo.remotes[0].name, "custom_remote")
 
+    def test_clone_with_credentials(self):
+        credentials = pygit2.UserPass("libgit2", "libgit2")
+        repo = clone_repository(
+            "https://bitbucket.org/libgit2/testgitrepository.git",
+            self._temp_dir, credentials=credentials)
+
+        self.assertFalse(repo.is_empty)
 
     # FIXME The tests below are commented because they are broken:
     #