Add support for head_repo param for PR creation

src/github3/repos/repo.py

@@ -1162,7 +1162,13 @@ def create_project(self, name, body=None):
 
     @decorators.requires_auth
     def create_pull(
-        self, title, base, head, body=None, maintainer_can_modify=None
+        self,
+        title,
+        base,
+        head,
+        head_repo=None,
+        body=None,
+        maintainer_can_modify=None,
     ):
         """Create a pull request of ``head`` onto ``base`` branch in this repo.
 
@@ -1171,7 +1177,9 @@ def create_pull(
         :param str base:
             (required), e.g., 'master'
         :param str head:
-            (required), e.g., 'username:branch'
+            (required), e.g., 'username:branch' or 'branch' when using head_repo
+        :param str head_repo:
+            (optional), required for cross-repository pull requests if both repositories are owned by the same organization. e.g., 'organization/repository'
         :param str body:
             (optional), markdown formatted description
         :param bool maintainer_can_modify:
@@ -1185,6 +1193,8 @@ def create_pull(
         data = {"title": title, "body": body, "base": base, "head": head}
         if maintainer_can_modify is not None:
             data["maintainer_can_modify"] = maintainer_can_modify
+        if head_repo is not None:
+            data["head_repo"] = head_repo
         return self._create_pull(data)
 
     @decorators.requires_auth

tests/integration/test_repos_repo.py

@@ -481,6 +481,28 @@ def test_create_pull(self):
 
         assert isinstance(pull_request, github3.pulls.ShortPullRequest)
 
+    def test_create_pull_head_repo(self):
+        """Test the ability to create a pull request by fully specifying the organization, repository, and branch."""
+        self.token_login()
+        cassette_name = self.cassette_name("create_pull")
+        with self.recorder.use_cassette(cassette_name):
+            original_repository = self.gh.repository(
+                "github3py", "github3.py"
+            )
+            repository = original_repository.create_fork(
+                organization="testgh3py"
+            )
+            pull_request = repository.create_pull(
+                title="Update forked repo",
+                base="master",
+                head="develop",
+                head_repo="testgh3py/github3.py",
+                body="Testing the ability to create a pull request",
+            )
+            repository.delete()
+
+        assert isinstance(pull_request, github3.pulls.ShortPullRequest)
+
     def test_create_pull_from_issue(self):
         """Verify creation of a pull request from an issue."""
         self.token_login()