find . -name .DS_Store -print0 | xargs -0 git rm --ignore-unmatch
Also add “.DS_Store” to your git “.gitignore” file
git add .gitignore git commit -m '.DS_Store bye bye!'
UPDATED
You might want to exclude some file for a specific repository then you can use:
your-repo/.git/info/exclude
In case you want to exclude files globally, in the root create:
.gitignore_global