Creates a link to the upload page. See WikiAttachments.
Why would you use this instead of a standard anchor? The UploadLinkTag automatically adds things like the correct class information (for styles), the jspwiki.baseURL property, attachment links, etc.
<wiki:UploadLink page="<page name>" format="anchor|url"> Link text </wiki:UploadLink>
<wiki:UploadLink>Upload a new attachment</wiki:UploadLink>.