MagicMaker2oo2

Hello, I am beeing curious about how you guys managed to modify the location and the name of the original .minecraft folder. I have red a lot about this and most of the time i can see people talking about temporarily changing the %appdata% environement variable value. I have also seen people talking about changing some lines of code in a decompiled version of the minecraft.jar file. Could someone enlighten me about how this is done specifically with technicpack modpacks please ? PS : i am hoping i posted this in the right section, if not i'm sorry and apologize.