How does a contributor who is not a committer merge a change?

[David Van Couvering]

http://wiki.apache.org/db-derby/MoveAChangeBetweenBranches
is very helpful, but is focused on the steps a committer would take.

Is there a process for a contributor who is not a committer to merge a 
change and then submit a patch for the merge?  Or is this something that 
can only be done by a committer?

Thanks!

David