Repository GUIDs again

Hey there folks, while mucking with the issue# 1003 branch I got sick
and tired of how we currently need to manually remember merges. I'd like
to tweak svn_client_merge to help me out here, but I have a problem.
Namely, that the URL syntax for "svn merge" requires that I need our
famous repository GUID to record the merge history correctly.
 
So could somebody pick a way to get the GUID into Subversion in a way
that it's not changeable and that svn_client_merge can acquire that
data? That way I can worry about recording this important merge source
information.
 
Getting this change in before 1.0 will allow us a chance in hell of
making better use of the information in the future.
 
Thanks,
Bill

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Do you want a dangerous fugitive staying in your flat?
No.
Well, don't upset him and he'll be a nice fugitive staying in your flat.