git-svn: svn (command-line) 1.0.x compatibility

Tested on a plain Ubuntu Warty installation
using subversion 1.0.6-1.2ubuntu3

svn add --force was never needed, as it only affected
directories, which git (thankfully) doesn't track

The 1.0.x also didn't support symlinks(!), so allow NO_SYMLINK
to be defined for running tests

Signed-off-by: Eric Wong <normalperson@yhbt.net>