My colleague, NM, recommended this course $$$:
Git & GitHub – The Practical Guide
Learn Git & GitHub and master working with commits, branches, the stash, cherry picking, rebasing, pull requests & more!
Git and GitHub Tutorial for Beginners [11 Hours], YouTube (11:12:59) by Bogdan Stashchuk (who additionally has a $$$ course)
Git Immersion (“a guided tour that walks through the fundamentals…”)
Git Anatomy by Dino Esposito at Redgate
Git Internals by Scott Chacon at PeeCode Press {now PluralSight} (121pp)
Pro Git by Scott Chacon and Ben Straub by Apress (free ebook)
Version Control with Git by dbt (I really like this workflow diagram they created) 
Git, GitHub, & Workflow Fundamentals by Molly Nemerever (I like the diagram she posted, too)
And she refers to this site, Getting Started with Git by Josh Errickson also
Git Workflows for Pros: A Good Git Guide by Joe James (contains several team workflow diagrams to consider)
Git cheatsheet from PhoenixNAP 
Git cheatsheet from Intellipaat 