Question [Q] Re sync ROM repo after changes have been made locally

Hi everybody,

I love SlimKat ROM for nexus 5 but for me, the lack of the new cm theme engine is annoying ! So what I'm going to make is to clone the Slim repo on my Ubuntu machine, clone the theme engine commit from the Paranoid Android gerrit and build it.

I've already learned how to cherry-pick and resolve conflict etc... but what I don't know is how to re-sync the Slim repo after some changes have been made locally on my computer ! If I remember well (when I was building PA for my old mako), when we modify some files locally, the sync command would failed because of the changed files, so how can I do for keeping the ability to sync my local source when I have changed/added some files ?

I've already searched around the web for how to do this and I've found that we can create gitignore file for ignoring files/folder during sync (correct me if I'm wrong !) but it work for the files that are on the Slim repo and that I have to modify for the theme engine, I mean during the sync command they are eventually modified but by keeping my change?

I hope my explanation is clear and sorry for my bad english, French is my native language !
Thanks in advance for your help ! And sorry if this is not the correct place for my question !
[CENTER]Actual phone:Nexus 5, Unlocked bootloader, Rooted (yes because a nexus without root isn't a nexus !)
ROM:Multirom with Primary => Mahdi, Secondary => SlimKat, Third => Ubuntu Touch
Kernel: For the moment Franco, but I often swith with ElementalX

My Guide:
[GUIDE]How to S-Off your HTC ONE M7 if you had issues with hboot 1.55 and OS 3.63.73

You're a UV/OC fan ? Take a look at this ! Very useful post