From what I have read, when merging SVN before 1.4 I have to do this “by hand” because the previous-merge info is not available:
svn merge svn://server/repo/trunk@revision svn://server/repoo/branch .
Since this is the first time I am merging what do I put in revision? Do I use the one at “branch time”?
Also, is there any way of doing this within the Eclipse-Collabnet client or do I have to do it via Tortoise?
The command to use is explained in the SVN book. Assuming you started your maintenance branch at revision 341, and the trunk is at revision 405, and the working copy is pointing to the trunk, the command should be:
svn merge -r 341:405 http://svn.example.com/repos/calc/branches/my-maintenance-branch
Remember that a merge consists in applying a diff from point A to point B into the working copy. Here, points A and points C are in the same branch: the maintenance branch: all the changes you made in this branch must be reapplied on the trunk.