In order to move a wiki into another one, you have to move:

  * data/pages/thing to data/pages/projects/thing
  * data/media/thing to data/media/projects/thing
  * data/attic/thing to data/attic/projects/thing

Upgrade then move stuff. That will split the changelog into *.changes files in the data/meta/ directory. Just remember to also move: 

  * data/meta/thing to data/meta/projects/thing