[Svnmerge] Branch to Branch to Trunk Merging

[Irvine, Chuck R [EQ]]

Our branching model is to always have the latest release (R) on the
trunk. Whenever we start on release R+1, we create a release branch for
R and let R+1 development proceed on the trunk. Say we have three
releases (R1, R2, and R3). Our branching structure would be:


             /---------------------
            / R1
           /
          /            /---------------
         /            /  R2
        /            /
-------/------------/-------------------
R1        R2          R3

Where R1 is on the top (oldest) branch, R2 is on the middle (newest)
branch, and R3 is on the trunk. We want to periodically merge R1 to R2,
and R2 to R3 (trunk). The documentation is pretty clear on how to merge
from the branch to the trunk. However, I can't figure out how to use
svnmerge to merge the the R1 branch to the R2 branch. 

Guessing from the info provided in the wiki, I perfored the following
(which didn't work):

1. I did a fresh checkout of R2. 
2. I Invoked svnmerge init <URL to R1>
3. Checked in from R2 dir the svnmerge-commit-message.txt message.
4. From top level R2 dir, invoked "svnmerge.py merge --bidirectional

This didn't merge anything at all into my R2 workspace.

Help on getting this figured out would be greatly appreciated!

Thanks,
Chuck