git-svn very slow on fetch (shared git-svn repo)

Here is the problem.

Doing a:

    $ git svn fetch

Takes age to update the repository. The long story is that I'm trying to have shared git-svn repositories.

I'm cloning the repository on a server using a standard "git svn clone". I then let users cloning this repository using the procedure described in git-svn help. Copy/paste here:

<<
        # Do the initial import on a server
                ssh server "cd /pub && git svn clone 
http://svn.example.com/project
        # Clone locally - make sure the refs/remotes/ space matches the 
server
                mkdir project
                cd project
                git init
                git remote add origin server:/pub/project
                git config --add remote.origin.fetch 
'+refs/remotes/*:refs/remotes/*'
                git fetch
        # Create a local branch from one of the branches just fetched
                git checkout -b master FETCH_HEAD
        # Initialize 'git svn' locally (be sure to use the same URL and 
-T/-b/-t options as were used on server)
                git svn init http://svn.example.com/project
        # Pull the latest changes from Subversion
                git svn rebase
 >>

If you do a "git svn fetch" (to get new branches) it takes age if you have imported branches that are not used since a long time.

I've traced this down to the Perl fetch_all procedure. It seems that the fetch is looking at the older version in all branches and then read the remote repository starting from this revision. As some branches are unused since a very long it it re-read most of the history. In my example it start at rev 8200 whereas the last revision on trunk is 150000 (I put trace in git-svn Perl script).

I have observed that this happen only the first time.

This can be confirmed by the fact that if you break git-svn fetch process and restart it it will start to a later revision. So it seems that git-svn is keeping some kind of data about what has already been fetched but those data are not properly copied by the procedure above.

Is there a workaround that? Where are those data stored?

Any guidance would be very welcomed.

Thanks, Pascal.