How would i make a map with multiple people?

[IdotKid]

I dont know if this is even possible, but given theres multiple people in credits of certain maps, I'm just asking to see if its possible, and if so, how?

 

[Crash]

There are other tricks you can do, but usually with my collaborative projects we just pass the VMF file back and forth.

 

[Muddy]

I use Dropbox, which has live file updating.

Also official map credits don't specify who did what, so it's likely some of the people credited didn't work on the map directly, but instead made some custom models, made the gamemode logic, did some voice acting etc.