tar cvzf somefile.tar.gz `svn stat | awk '{print "test -f " $2 " && echo " $2}' | bash`

Word.

To break it down:

The svn stat command is getting all the files that have changed obviously.

The awk command its piped to is the real part that’s doing the work.  The awk command prints

test -f file && echo file

Pipe that through bash, and you have commands, which essentially will echo the file if the file is a file. Simple? No? I mean, it will not print it out if it’s a directory, so you don’t have to worry about it adding entire directories.

Surround that whole thing in backquotes (that’s the one with the tilde (that’s the one next to the ‘1′ key ( I’m not telling you where the ‘1′ key is)))  and give it as the argument to the tar command.