New returns a new lock file at the given path.

ErrBusy means the lock is being held by another living process.

ErrInvalidPID means the lock file contains an incompatible syntax.

ErrProcessDead means the lock is held by a process that does not exist.

ErrRogueDeletion means the lock file was removed by someone other than the lock holder.

Lockfile is a process-based file lock.