Question about merging differences between revisions from main trunk to branch

[Michael Sims]

I'm probably not RTFM'ing hard enough, but I can't seem to figure this out.

I know, or at least it is my understanding, that I can merge the 
differences between two revisions (by rev number, not by tag) from a branch 
to the main trunk fairly easily like so (assuming my working directory is a 
checked out module from the main trunk):

address@hidden main_co_files]$ cvs update -r BRANCHNAME -j 1.1 -j 1.2 
index.php

My question is, what if I'm currently in the BRANCH, and want to merge the 
differences from the main trunk.  If I do this:

address@hidden branch_co_files]$ cvs update -j 1.1 -j 1.2 index.php

It will merge the changes between these files on the BRANCH, not from the 
main trunk.

I can work around this problem if I had the foresight to give both 
revisions symbolic tagnames, but I don't know how to do it if I just have 
the rev numbers.

I guess my question is, is there a default BRANCH tag for the main 
trunk?  HEAD seems to refer specifically to the latest revision on the main 
trunk, not the entire trunk itself.

Am I missing something really obvious, or do I need to go back and read the 
manually more carefully? Any help, pointers, or flames are welcome.