Sorry to necro this thread but look into diffing/patching tools such as this one. There are several formats the most common contains a bit of context sorounding the changes (it is still a derivative) but it won’t redistribute any unchanged original assets and not enough information to reproduce the original unless like almost every line is modified. See Wikipedia for more details. Adding a new menu option for a new path should hardly contain much of the original conversation. This tool can also patch folders and stuff so it would be suited for IMHO.
Would the developer feel comfortable with this?