title: Migrating multiple versions of a Userscript into a single version
body: <p>The main question I have is: <em>What is the unique identifier that userscript managers use to decide if this script you are installing is a new version of one you already have or a completely different script?</em></p>
  
  <p>The situation: I had two versions of a userscript one for FF and one for Chrome on the now closed down userscripts.org, with different names. I have a user base with these installed. I have completely reworked the script, and plan on integrating them into a single script for all browsers. How can this be done while allowing my users to install over their old scripts, retaining their saved GM_Values?</p>
  
  <p>Is it just the name? do I just submit the script twice with different names? Can the updateURL/downloadURL point to a different source than the installing script? That sounds like a pretty big security whole, if so. But if I could just creates two ~identical~ scripts with different names, point both to update off the main one, so I can phase out the old "My Script (FF)" script (it would just be a way to migrate Firefox users over to the main branch). Or am I going about this all wrong?</p>