Enabling git checkout support for GitHub

Over the past week, Spacelift customers have been impacted by various GitHub incidents that have resulted in Spacelift not being able to download the source code for stacks and modules. Although these incidents are not directly related to any changes within Spacelift, this is causing Spacelift customers to experience intermittent issues executing runs and deploying new module versions, and we have been investigating what we can do to mitigate the problems.

We have raised a support issue with GitHub to try to work with them to resolve the problems, but in the meantime we want to provide a potential fix for customers who are experiencing issues.

Currently Spacelift uses the GitHub API to download the source code for stacks/modules as a tarball, but we have introduced experimental support for using standard Git cloning instead. We are initially introducing this on an opt-in basis so that affected customers can decide on a case-by-case basis whether to enable the feature. We believe that this may be a viable approach because based on our observations and customer feedback, core git functionality in GitHub does not appear to be impacted as much as downloading code via the API.

Initially we want to provide this functionality on an opt-in basis, but assuming it's working well, we will roll it out to all customers. We will provide a further update before that process begins.