This would checkout a specific branch like /devopstools that performs steps in the CI that do not require the entire branch.
For example, if your repo has these branch sizes.
/dev is 6GB
with a job step like - checkout: "devopstools" we can checkout out our tools only and save a LOT of bandwidth via unnecessary cloning. Some of the jobs are just figuring out what version number or job to run next and doesn't need all the repo just a few files I can get with a git command like.
git checkout commit_hash filetocheckout