how to make copy of branch in git

C++
git checkout -b new_branch old_branch
# initial state 
commit 2 (65bc341)   O  <-- master
                     |
     (more commits) ...
                     |
commit 1 (125afe4)   O  <-- origin/master

# run command
git push origin 125afe4:refs/heads/master-copy

# result
commit 2 (65bc341)   O  <-- master
                     |
     (more commits) ...
                     |
commit 1 (125afe4)   O  <-- origin/master origin/master-copy
Source