With the release of Dynamics NAV 2015, Microsoft introduced the PowerShell upgrade that automates the code merging as well as the data upgrade. In order to take advantage of the PowerShell upgrade process, you need to be at least on Dynamics NAV 2013.
There are some limitations to the automated upgrade. This is listed on MSDN at https://msdn.microsoft.com/en-us/library/mt600251(v=nav.90).aspx.
Basically, what it says is the following: