emacs-backup-file

Automatically back up all changes made from emacs to a git repo in ~/.backups

To use:

(require 'backup-file)
(add-hook 'after-save-hook 'backup-file)
(define-key global-map (kbd "C-c b") (function backup-file-log))
;; Or another key of your choosing

The repo in ~/.backups might eventually get really big so it might be a good idea to have a cronjob or something do something along the lines of this, e.g. in a cronjob

cd ~/.backups
commit=$(git log --since="1 week ago" --reverse --pretty=%h | head -n1)
if [ -n "$commit" ]; then
   git checkout --orphan temp_remove_old_history "$commit"
   git commit -m "Truncated history" --allow-empty
   git rebase --onto temp_remove_old_history "$commit" master
   git branch -D temp_remove_old_history
   git prune --progress
   git gc --aggressive
fi

You can also now also do this from elisp using:

(backup-file-truncate-history)

Example:

https://www.youtube.com/watch?v=NwdRFmVhEIo&feature=youtu.be