Issue cloning large repositories

[MichaelMackus]

I had an issue in cloning large repositories. Took me a little while to track down (learned some more bash along the way), and I've created a fork which basically disables cloning the entire revision history for SVN externals. This allows large repos (like Symfony projects) to be cloned without waiting hours for everything to be indexed.

Just in case anybody had the same issue: https://github.com/MichaelMackus/git-svn-clone-externals

[MichaelMackus]

This would probably be best implemented as an "option" passed to the command but I didn't have time to do that.

I also added another sed command to fix weird SVN paths like: /path/URL path2