prereceive

Prereceive, often written prereceive (or pre-receive), refers to a server-side hook in Git that runs when a client pushes changes to a remote repository. It is invoked on the receiving end before any refs are updated, allowing the server to enforce policies or reject a push before data is written. The hook is typically implemented as a script named pre-receive (or prereceive) located in the repository’s hooks directory on the server.

During execution, the prereceive script reads lines from standard input, each containing old-value new-value ref-name. These lines describe the proposed updates for each ref. The hook can inspect the incoming changes, perform checks, and decide whether to accept or reject the push by exiting with a non-zero status and emitting messages to standard error. If any line is rejected, the entire push is rejected and no refs are updated; if all lines are accepted, the push proceeds and refs are updated.

Prereceive is complemented by other server-side hooks such as update (which runs once per ref) and post-receive (which runs after all updates, typically for notifications or secondary processing). Together, these hooks enable comprehensive validation and workflow enforcement on the server.

Common uses include enforcing commit message formats, blocking certain file types or large binaries, preventing force pushes or branch deletions without approval, and integrating external policy checks or security controls. Implementations vary by hosting platform, but prereceive scripts generally require a Unix-like environment and familiarity with shell scripting and repository administration.