We are in the processes of changing the SimpleITK development workflow to use the a full Github workflow, with the merge button. Please pardon our dust and delays in merging as we update the services, configuration scripts, and documentation.
A quick update: Github is now the official upstream for SimpleITK. Also the Utilities/SetupForDevelopmentScript.sh has been updated to configure your check out to use the appropriate repositories for developments.
Additionally, we have enabled the Github merge button after the cross platform CI has passed and a review.
We still need to update the documentation, but if you are familiar with the ITK workflow or the general GitHub workflow you are all set.
Lastly, thanks for Kitware for hosting SimpleITK on itk.org, and for assisting with the transition.