How are extended Fiori apps deployed?

I have imported a Fiori app into the SAP WebIDE and made my changes. What is the process to deploy it back to the ABAP repository on the gateway server?

I'm under the impression the extensibility points are to allow you to only change the parts you need, rather than creating a z copy program. These changes then get merged with the standard app to present the modified version.

So how do I merge my changes with the standard app? Do I still need to create a z program? If so, why do I bother with extension points in the first place instead of just making changes to the code normally.

Thank you.