pre-lock — Notification of a path lock attempt.
The pre-lock hook runs whenever someone attempts to lock a path. It can be used to prevent locks altogether, or to create a more complex policy specifying exactly which users are allowed to lock particular paths. If the hook notices a pre-existing lock, then it can also decide whether a user is allowed to “steal” the existing lock.
If the pre-lock hook program returns a non-zero exit value, the lock action is aborted and anything printed to stderr is marshalled back to the client.