Support for create_fork (#1306)

* Support for create_fork

http://developer.github.com/v3/repos/forks

* Add test case for create_fork

* Add param doc and fix extra line

* Specify the organization to increase line coverage

* Update test data

* Add type assert for organization param

github/Repository.py

@@ -1867,6 +1867,23 @@ class Repository(github.GithubObject.CompletableGithubObject):
             None
         )
 
+    def create_fork(self, organization=github.GithubObject.NotSet):
+        """
+        :calls: `POST /repos/:owner/:repo/forks <http://developer.github.com/v3/repos/forks>`_
+        :param organization: string or "none" or "*"
+        :rtype: :class:`github.Repository.Repository`
+        """
+        assert organization is github.GithubObject.NotSet or isinstance(organization, (str, six.text_type)), organization
+        post_parameters = {}
+        if organization is not None:
+            post_parameters["organization"] = organization
+        headers, data = self._requester.requestJsonAndCheck(
+            "POST",
+            self.url + "/forks",
+            input=post_parameters,
+        )
+        return Repository(self._requester, headers, data, completed=True)
+
     def get_git_blob(self, sha):
         """
         :calls: `GET /repos/:owner/:repo/git/blobs/:sha <http://developer.github.com/v3/git/blobs>`_

tests/Repository.py

@@ -370,6 +370,9 @@ class Repository(Framework.TestCase):
     def testGetForks(self):
         self.assertListKeyEqual(self.repo.get_forks(), lambda r: r.owner.login, ["abersager"])
 
+    def testCreateFork(self):
+        self.assertEqual(self.repo.create_fork("prtg-dev").full_name, "prtg-dev/PyGithub")
+
     def testGetGitRefs(self):
         self.assertListKeyEqual(self.repo.get_git_refs(), lambda r: r.ref, ["refs/heads/develop", "refs/heads/master", "refs/heads/topic/DependencyGraph", "refs/heads/topic/RewriteWithGeneratedCode", "refs/tags/v0.1", "refs/tags/v0.2", "refs/tags/v0.3", "refs/tags/v0.4", "refs/tags/v0.5", "refs/tags/v0.6", "refs/tags/v0.7"])