In the current API (2.1 and 2.2), how do you get questions that have a specific tag or tags?

EG:

1. All Stack Overflow questions asked in the past 2 months tagged 'ruby'?
2. All Stack Overflow questions asked in the past 2 months tagged 'ruby' and 'git'?
3. All Stack Overflow questions asked in the past 2 months tagged 'ruby' or 'git'?