I'd like to separate the modded game from the vanilla one so I researched and I found that Technic pack guys managed to do it changing some things in the Minecraft.java file.
I installed MCP and Forge as stated in the Readme file and then i went to the file and did the changes they say here: https://raw.github.com/TechnicPack/Technic/master/modfixes/How%20the%20Fuck.txt
I recompiled and took the Minecraft.class from the bin folder of MCP to the /net/minecraft/client folder of minecraft.jar
Result: black Screen
To remove a possible typo I recompiled (in a new isntalation of MCP) without editing anything and the result was the same.
Can someone help me, please? If that fix could be added to Forge it would be great.
I mean so the game isn't hardcoded to %appdata%/.minecraft but to read where the minecraft.jar is so I can install the game to, for example, %appdata%/.modedmc