First try at merging a branch back into the trunk. A simple case because no changes were made to the trunk while working with the branch.

In the branch working dir:
svn log -v --stop-on-copy

This reports the list of revisions since the branch was created. This range of revisions is used as an argument to the merge command.

Create a clean trunk working dir and this issue these commands:
svn merge -r 11:15 http://../branches/css-1024px
svn diff -r 15 http://../branches/css-1024px
svn commit

Next, switch my development and reference working directories back to pointing at the trunk:
svn switch http://localhost/svn/ll/trunk

Lastly, there were a bunch of tmp files in my working directory, so I tried out svn cleanup which removed them.