Again the official force.com documentation for the Migration Tool is lacking here. This is a good link to illustrate the options that are missing the official doc.
Also one more thing to keep in mind. WorkflowRule is one component that you're allowed to use any visible character as the name. However you should not do that for the sake of using the Migration Tool, because it will URL encode (almost) all the special characters. Space, dash, and underscore are OK, but parenthesis becomes %28 and %29 in your retrieved components. This then would not match your package.xml, which causes an error when you deploy. So, stay away from special characters in your names, even when you are not forced to by the UI. The same goes with Layout names.