Making the "Copy Branch" menu option work was a treat.
requestHelper() invokes an asset helper via AJAX.  processPlugin() handles the JSON responses, which in this case is to open a dialog box and show
a given URL in it (openDialog key in the JSON hash).  that pop-up is open and the page loaded, and that displays a form.  that form submits
to an asset helper (uh oh) which also returns JSON (actually, it was failing to do even that and was stringifying a hash).  even if it returned
JSON, it would just get shown to the user in the pop-up.  so the form that gets loaded into the pop-up has to, onsubmit, after it has config
details from the user, run JS to make the AJAX request to the asset helper to start the actual copy operation, call into the admin's JS to
pop up the dialog that polls on a forked process, and then call into the admin to close itself.  this is a nasty hack that daisy chains
together two possible replies to processPlugin(), one after the other.