maps: do not ask sqlite for row count "SELECT COUNT(1) FROM x" is not O(1) for sqlite and can be slow on large tables. This patch changes the count to be backed by a file instead. The change exposes a risk that the number may become inaccurate, if __setitem__ is called with a same key multiple times. But we don't do that during pull, and only use __len__ to calculate how many revisions pulled, or test if the map is empty. So it would be fine.

#!/bin/sh
mkdir temp || exit 1
cd temp
svnadmin create repo
svn co file://`pwd`/repo wc
pushd wc
mkdir -p project/trunk
svn add project
svn ci -m 'trunk'
cd project/trunk
echo a > a
mkdir narf
svn add a narf
svn ci -m 'file and empty dir'
popd
svnadmin dump repo > ../empty_dir_in_trunk_not_repo_root.svndump
echo 'dump in empty_dir_in_trunk_not_repo_root.svndump'
echo 'you can probably delete temp now'