Disable git-svn support by default. If you really want to use it, set

the git configuration variable dune.autoupdate to "true", for example by

  git config --add dune.autoupdate true

in the directory of the repository which you want to enable auto
updating for.

I will leave FS#479 open, because git-svn support still is broken.


[[Imported from SVN: r5393]]