I have to work with customized magento 18.104.22.168 of my client. It is customized also in some part of core....
Do you know what can be the best way to upgrade this installation to 22.214.171.124 version?
Exist some kind of patch (git or script) that can show me a list of modified files?
You can use some tool to compare code (for example, on Linux, you can use Meld) from two files or directories.
You could compare the project code with a clean isntance (same version with the same patches applied).
thank you for your answer.
Ok your solution to check the difference among files modified in the core.
For upgrade the magento version do you advice a clean installation applying only custom modules and theme? Or with magento connect? or something else?
Magento connect shouldn't be an option (I didn't tried because I've used MC just a few time in 10 years) since was disabled on September 15th. But to be honest, I didn't try to perform an upgrade in that way for many many years.
About how to proceed it will depend on your base code, the customizations and your time. Maybe you can sanitize the core and then apply the new files over your current instance. (Of course test all this steps on a safe envirnment first and make a backup always).
If you don't mind the old data you can start fresh. But again, it will depend on your requirments and deadlines.
(my 2 cents)