How do I 'overwrite', rather than 'merge', a branch on another branch in Git?

Question

I have two branches, email and staging. staging is the latest one and I no longer need the old changes in email branch, y

Answer 1

I wanted to merge two branches so that all the contents in old_branch to be updated with the contents from new_branch

For me this worked like a charm:

$ git checkout new_branch
$ git merge -m 'merge message' -s ours origin/old_branch
$ git checkout old_branch
$ git merge new_branch
$ git push origin old_branch