Prepush

Prepush, or pre-push, refers to a Git client-side hook that runs during git push before any changes are transmitted to the remote repository. It is executed on the local machine after the remote is contacted but prior to updating the remote refs. The hook is implemented as an executable script named pre-push stored in the repository’s .git/hooks directory.

During a push, Git passes information about what is being pushed to the hook via standard input. Each line corresponds to a ref being pushed and has the format: local_ref local_sha remote_ref remote_sha. The hook can read these values to decide whether to allow the push to proceed. The hook's exit status determines the outcome: exit with code 0 to continue the push, or a non-zero exit to abort the push. The hook may also print messages to standard output or standard error to inform the user of reasons for rejection.

Typical uses for pre-push include running a test suite, performing lint or security checks, validating commit messages, or ensuring that sensitive data is not inadvertently pushed. Because it runs locally, it helps enforce quality gates before code leaves the developer’s environment. However, since it is a client-side mechanism, its enforcement is limited to the machine where the hook is installed and can be bypassed with options such as git push --no-verify.

In addition to pre-push, Git offers server-side hooks like pre-receive and update for enforcing policies on the remote side. The pre-push hook complements these by catching issues before the push leaves the developer’s workstation.