Answers for "what to add to gitignore"

git add gitignore

$ touch .gitignore

how to put files into gitignore

$ echo debug.log >> .gitignore
$ git rm --cached debug.log
rm 'debug.log'
$ git commit -m "Start ignoring debug.log"

what to add to gitignore

Look at this awesome site!
https://www.toptal.com/developers/gitignore
Generates a gitignore for you, based on the technologies you're using

what is add.gitignore

The purpose of gitignore files is to ensure that certain files not tracked by git remain untracked.