This command runs a user-specified command while locking the repository. For example:
$ BORG_REPO=/mnt/borgrepo borg with-lock rsync -av /mnt/borgrepo /somewhere/else/borgrepo
It will first try to acquire the lock (make sure that no other operation is running in the repo), then
execute the given command as a subprocess and wait for its termination, release the lock and return the
user command's return code as borg's return code.
NOTE:
If you copy a repository with the lock held, the lock will be present in the copy. Thus, before using
borg on the copy from a different host, you need to use "borg break-lock" on the copied repository,
because Borg is cautious and does not automatically remove stale locks made by a different host.