maps: add the "branchmaxrevnum" method to RevMap Iterating the RevMap can be very expensive for large repos. To prevent future code from iterating the possibly huge RevMap causing performance issues, it's a good idea to clean all iterating code outside RevMap. This patch adds a method used by "get_parent_svn_branch_and_rev". In the future, we will have a SqliteRevMap, which will have an efficient implementation for this query, and it will disable "__iter__" to prevent future performance issues.

#!/bin/sh
mkdir temp
cd temp
svnadmin create repo
svn co file://`pwd`/repo wc
cd wc
mkdir branches trunk tags
svn add *
svn ci -m 'btt'
cd trunk
mkdir narf
cd narf
for a in alpha beta gamma delta ; do
    echo $a > $a
done
cd ..
svn add narf
svn ci -m 'Add files.'
cd ../../..
svnadmin dump temp/repo > file_not_in_trunk_root.svndump
echo
echo 'Complete.'
echo 'You probably want to clean up temp now.'
echo 'Dump in file_not_in_trunk_root.svndump'
exit 0