I use Beyond Compare to help me through the process of updating packs I've customized. I'm sure there are other programs out there that work similarly. WinMerge, mentioned by @Jnelso99 above, sounds like one, I'm just not familiar with it. Once you see how the process works it becomes much more manageable. I can update a pack and check it now in less than half an hour usually. As a bonus, I've also found that I understand the mods a little better by looking that the new changes as they come into the config files.
- Backup pack folders
- Download new pack (Note: Due to my limited bandwidth I actually make a backup of the newly updated folders, too. I simply can't afford to download twice!)
- Use Beyond Compare on the /mods and /config folders.
- From the results window in BC pay special attention to differences. (I choose to copy my changes into the newly updated folder and my examples will follow that logic.)
- Mods folder: be sure the newest versions are in the right places and that nothing is duplicated. Copy in any mods I've added. BC will show when a file is in one folder not the other.
- Config folder: open any files with differences, jump to the next highlight difference line, choose if you can ignore or not.
- Example 1: If the line is a block id you've changed, copy that line over.
- Example 2: If the line is new config settings be sure it stays in.