import clr
clr.AddReference("SharpSvn")
import SharpSvn,System

message = "some useful commit message why you created the branch"

args = SharpSvn.SvnCopyArgs()
args.LogMessage = message

source = SharpSvn.SvnTarget.FromString("svn://localhost/testrepo/trunk/FooTest")
dest = System.Uri("svn://localhost/testrepo/branches/fooBranch")

client = SharpSvn.SvnClient()
client.RemoteCopy(source, dest, args)