For all of you that are trying to install git-svn on your machine: Quite a while ago the git folks reorganized the command line interface, and what used to be called “git-<whatever>” is now called “git <whatever>” . Note the subtle difference here? So if you are looking for the git-svn binary on your machine: there is none.
git-svn is still part of the git-core. Chances are it is installed on your machine alongside git. If not, and you are on a Mac, you install it via “port install git +svn”
It is as easy as this, and it took me hours to find out. Someone should have said this, and someone who said it should have received a better Google ranking.