We’ve been part of the beta of GitHub Actions since the beginning, following its development closely and testing it on a lot of smaller repositories in our organization, and we’re really satisfied so far with the product. GitHub Actions provides most of the features we love about Azure Pipelines, while being integrated with GitHub’s UI, permissions and workflows.
GitHub has also offered to sponsor a dedicated pool of builders with increased resources. Our extensive but time-consuming CI is one of the major pain points for compiler contributors, and the additional resources have the potential to drastically improve our developers’ experience. We have achieved 60% faster builds in preliminary testing thanks to the increased core count in the dedicated builder pool, and there is still large room to parallelize and finish builds even faster.
Our plan is to start running GitHub Actions in parallel with Azure Pipelines in the next few weeks, and we’ll keep the community updated as we learn more.
[Update] Some members of the community asked why we're considering to switch away from Azure Pipelines so soon after migrating to it. We want to reaffirm that we're happy with Pipelines as a product, but both Microsoft and GitHub asked us to try GitHub Actions because it's more closely integrated into the GitHub workflow that we already use. After we used it for a while in other repositories we were satisfied enough to start evaluating a migration for rustc's CI.