[Svnmerge] Why does svnmerge avail only work on working directories?

[Mattias Brändström]

Hello!

I am trying to write a little bash script that will summarize what 
revisions for a number of projects (merging from multiple heads) that 
are available for merging. It looks like this right now:

#!/bin/bash

REPO_BASE=svn+ssh://design200/home/svn/

PROJECTS=(ttutil \
           touchcore \
           foo-repos)

for P in ${PROJECTS[*]}; do
   INTEGRATED=`svn propget svnmerge-integrated $REPO_BASE/$P/trunk`
   echo $P
   for I in $INTEGRATED; do
     BRANCH=${I%:*}
     AVAILABLE=`svnmerge avail \
                -S $REPO_BASE/$P/branches/$BRANCH \
                $REPO_BASE/$P/branches/$BRANCH`
     echo "  $BRANCH - $AVAILABLE"
   done
done

Now I have some problems. I would like to use a URL as argument to 
svnmerge avail instead of a PATH. svnmerge seems to only accept svn 
working directories as its last argument. Is there some special reason 
for this or would it be possible to change it to accept either a path or 
a URL?

Regards,
Mattias