Cherry-pick 277008@main (a1f01fd). rdar://125792901

    Github api should not assume the current user as the fork owner.
    https://bugs.webkit.org/show_bug.cgi?id=272054
    rdar://125792901 (Github api should not assume the current user as the fork owner)

    Reviewed by Jonathan Bedard.

    Canonical link: https://commits.webkit.org/277008@main

Canonical link: https://commits.webkit.org/272448.902@safari-7618-branch

Tools/Scripts/libraries/webkitscmpy/webkitscmpy/remote/git_hub.py

@@ -139,7 +139,9 @@ def create(self, head, title, body=None, commits=None, base=None, draft=None):
                 if not value:
                     raise ValueError("Must define '{}' when creating pull-request".format(key))
 
-            user, _ = self.repository.credentials(required=True)
+            if ':' not in head:
+                user, _ = self.repository.credentials(required=True)
+                head = '{}:{}'.format(user, head)
             url = '{api_url}/repos/{owner}/{name}/pulls'.format(
                 api_url=self.repository.api_url,
                 owner=self.repository.owner,
@@ -152,7 +154,7 @@ def create(self, head, title, body=None, commits=None, base=None, draft=None):
                     title=title,
                     body=PullRequest.create_body(body, commits),
                     base=base or self.repository.default_branch,
-                    head='{}:{}'.format(user, head),
+                    head=head,
                     draft=draft,
                 ),
             )