Using git as a backup tool without local .git folder

"I'd also suggest that you use a proper backup tool, such as rsync/rsnapshot (if you need the backed-up files to still be playable) or duplicity (if you don't). If you need to sync in both directions, or want to see what has changed before syncing, there's also unison, which I use to keep the music files on my Laptop in sync. Additional verification of file integrity could be done using a tool like md5deep, however you'd have to write wrapper-scripts yourself.

If you really, really want to use something git-based, you could look at gibak, which is a general-purpose backup-tool based on git. I haven't looked at it too closely though, so it might not be the right choice for you; I think you would still need to symlink the .git-directory for one."

git is for versioning files. If you just want a backup try rsnapshot.