It's actually pretty simple
What Minecraft does is it gets the value of the environmental variable APPDATA, then creates a folder .minecraft (or uses it if it's currently there) and uses and creates data there.
So basically, you just have to force a value to be sent to Minecraft when it requests for the environmental variable APPDATA, which can be done in Windows by set (and start to start minecraft).
So, for Windows users, you can use this template to change the minecraft data directory:


Here's mine for an example:

So, I set my APPDATA path to be the current directory of the .bat file, which means a .minecraft directory will appear in the same directory as the .bat. And, I run the Minecraft launcher (Minehack.jar) with javaw. It's important to do start because otherwise the value you specified for APPDATA won't be enforced on Minecraft (javaw).

See a lots of creative DS Hacking here
If you want to support me, you might check out my Patreon Page : )

Portable Minecraft.
You can move your data around with little effort from computer to computer.

The only problem is that you can't create a "Portable GPU" xD

I made portable minecraft, only to figure out It could not run anywhere because nobody had a good GPU... xD

I could probably play portable Minecraft at school, as I believe the school computers' GPUs can handle it... Sorta.

I don't know why I would want to do this, though.
Though, that is quite a nice tip if I'll ever need to do it.