[gitignore] .gitignore all the .DS_Store files in every folder and subfolder

Add**/.DS_Store into .gitignore for the sub directory


If .DS_Store already committed:

find . -name .DS_Store -print0 | xargs -0 git rm --ignore-unmatch

To ignore them in all repository: (sometimes it named ._.DS_Store)

echo ".DS_Store" >> ~/.gitignore_global
echo "._.DS_Store" >> ~/.gitignore_global
echo "**/.DS_Store" >> ~/.gitignore_global
echo "**/._.DS_Store" >> ~/.gitignore_global
git config --global core.excludesfile ~/.gitignore_global