To untrack a single file that has already been added/initialized to your repository, i.e., stop tracking the file but not delete it from your system use: git rm –cached filename
To untrack every file that is now in your .gitignore:
First commit any outstanding code changes, and then, run this command:
git rm -r --cached .This removes any changed files from the index(staging area), then just run:
git add .Commit it:
git commit -m ".gitignore is now working"To undo
git rm --cached filename, use git add filename.
Source: http://stackoverflow.com/a/1139797/3912326