workingDirectory is not honored when tagging

When using 'tag' I cannot set the 'workingDirectory' property in either the pom or command line.

I.E.
if my pom is not the directory I want to tag I cannot set the working directory to something else.

mvn scm:tag -DworkingDirectory=/tmp/somewhere

I believe that this should change directories to /tmp/somewhere and then perform the 'svn copy' command.