gh pr create fails in v2.64.0 if the current branch doesn't have the upstream configured #10188

Describe the bug

There appears to be a regression in v2.64.0 where gh pr create will now fail to create the PR unless the upstream is available via git config (basically requiring the -u option of git push). The error is aborted: you must first push the current branch to a remote, or use the --head flag from here.

Note I've already started a PR to fix this here: #10177

Internal tracking issue: https://github.com/github/cli/issues/730

Steps to reproduce the behavior

1. git checkout -B my-branch
2. Make some edit and git commit it
3. git push origin my-branch
4. gh pr create ...

Expected vs actual behavior

Up to and including v2.63.2 these commands succeed. In v2.64.0 it will fail with the above error.