usage: svnsync initialize DEST_URL SOURCE_URL
Initialize a destination repository for synchronization from
another repository.
If the source URL is not the root of a repository, only the
specified part of the repository will be synchronized.
The destination URL must point to the root of a repository which
has been configured to allow revision property changes. In
the general case, the destination repository must contain no
committed revisions. Use --allow-non-empty to override this
restriction, which will cause svnsync to assume that any revisions
already present in the destination repository perfectly mirror
their counterparts in the source repository. (This is useful
when initializing a copy of a repository as a mirror of that same
repository, for example.)
You should not commit to, or make revision property changes in,
the destination repository by any method other than 'svnsync'.
In other words, the destination repository should be a read-only
mirror of the source repository.