gistfile1.txt

# given two users, Bob and Sally, each with their own clone of a github repo and a share branch "foo"
# bob says "hold up don't push to github for a minute"
Bob   : git checkout foo ; git pull --rebase ; git rebase master ; git push
Sally : git checkout foo ; git pull --rebase
# and then they go back to work

If someone is feeling paranoid they can always git checkout -b backup_branch to keep a pointer to the old branch state before the rebase.

However, you can always pull out the commits from the ref log if all else fails.