Vim can view tar files (go ahead, open a tarball, it's pretty cool), it lets you navigate through the tarball and even open the files within. On linux systems I can edit these files and even save them! But on OSX I get an odd error:
***error*** (tar#Write) sorry, unable to update /ball.tar with file/in/tar.ball
Googling seems to fail me. In fact documentation I can find seems to indicate vim shouldn't even support editing these tarballs (though I can very clearly do it on multiple systems with the default vim installation).