[Svnmerge] Problem init'ing a branch of a branch

[Buddy Burden]

Guys,

I'm having a bit of trouble with svnmerge init.  Let me explain the situation.

First, I have my trunk, which is in /trunk.

Now, I create a branch, which is in /branches/sp3_alpha_branch.  I use
svnmerge init on this guy, and svnmerge merge (to pull changes from
the trunk) moderately regularly.  This goes _mostly_ well--I had some
problems on the last merge, but hopefully that isn't relevant here.

Next, I have to create a branch of the branch, which I call
/branches/sp3_iter4.  The reason I have to do this, even though my gut
tells me it's probably a bad idea, is that the original branch is
_almost_ ready for launch, but not quite.  It's going to final QA, and
can't be merged back into the trunk until that's complete.  However,
we have to code some further changes to this new functionality.  We
can't branch the trunk, because the functionality we want to extend
isn't _on_ the trunk.  We can't wait until after we merge to the trunk
because ... well, because management is impatient. :)  And there are
some legitimate business reasons, even.  So, against my better
judgement, I am convinced to branch the branch.

Next, the original branch is successfully merged back into the trunk.
Again, there were a few problems (e.g., conflicts in files that had
never been touched since the final merge from trunk to branch), but
nothing too awful and it's all good now.

So, _now_ what I want to do is merge the trunk into the second branch
(the branch of the branch, that is).  So I get myself a clean copy,
and I run svnmerge init:

[d-smo-devsandbox:~/proj/test_merge] svnmerge.py init
svnmerge: Repository-relative path /rent/branches/sp3_alpha_branch has
already been initialized at .
Use --force to re-initialize

And I don't know where to go from here.  I'm sort of scared to use the
--force switch.  I tried giving init the -r switch, with the revision
range of 1-NNN (where NNN is the revision number of the branch point;
basically exactly what the Wiki tells me to do for older versions of
svnmerge), but that doesn't help.  I see that I could supply SOURCE to
init, but what would I specify for the source?  The init command
doesn't seem to allow the -S switch (not that I'd know what to put for
that either, really).

Can anyone offer any help?

My svn client, BTW, is 1.3.1, although I also have a machine with
1.4.6.  I could definitely upgrade (client side only) to 1.5.x if that
is in any way helpful.

Hope someone can shed some light on this one ... TIA!


            -- Buddy