Atlassian tutorials: https://www.atlassian.com/git/tutorials
Github https://guides.github.com/
GitHub Learning Lab https://lab.github.com/
GIT Cheatsheets:
https://education.github.com/git-cheat-sheet-education.pdf
https://github.github.com/training-kit/downloads/github-git-cheat-sheet.pdf
Version Control with Git: https://swcarpentry.github.io/git-novice/