The workflow is: You create a git branch, commit your changes to it and push them to the repo server. The CI then checks whether the code is formatted as expected. If the code is incorrectly formatted, the CI job fails and prints the format error(s). When the code is formatted properly (no CI jobs fail), you are allowed to merge into the master branch.

Reading your comment I assume you want the repo server to reject incorrectly formatted code at push time. Rejecting commits/pushes has the disadvantage that you cannot share your code/branch with others (or yourself on other devices), and cannot back up your code to the repo server.

You could argue formatting doesn’t take long. I’d argue, the repo server shouldn’t keep me from publishing code to a dev branch.