What it is
An official GitHub Action that fetches a repository into the runner's workspace so later workflow steps can build, test, or deploy it. It supports picking a branch, tag, or commit, shallow or full history, sparse and partial clones, submodules, Git LFS, and authentication by token or SSH key. Developers writing CI/CD workflows on GitHub add it as the first step of nearly every job, and recent versions block unsafe checkouts of fork pull requests by default.