1. add a new branch
cd workspace
git branch user1/newbranch1
git checkout user1/newbranch1
or
git checkout -b user2/newbranch2
2. when user1/newbranch1 development finished, merge it into master branch.
git checkout master
git merge user1/newbranch1
delete branch user1/newbranch1
git branch -d user1/newbranch1