How to "force" ignore a file?

Question

I have this .gitignore:

django-countries/*
data.db
myproject/settings.py
myproject/wsgi.py
*.pyc

I need to ignore myproject/settings.py because they're different in the development environment and the production environment but git still tracks the file. I tried to ignore it in sourcetree but the option appears inactive. Any Ideas?

marcoslhc · Accepted Answer

I found the answer here http://stackoverflow.com/questions/1139762/gitignore-file-not-ignoring

Basically clean the index and cache, then ignore the file