I was trying to use the renameField function as outlined in the docs and found that it was missing! I was able to obtain the code from Trac, though I was under the impression that this should have been in 2.2.2:
It looks like matt has just recently added it on that custom branch. I think I added that to the docs after I found that in the code while working on that 2.2.2assets branch... It will be part of 2.2.3 or whenever we merge the changes from that branch.