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

If you just want the two branches 'email' and 'staging' to be the same, you can tag the 'email' branch, then reset the 'email' branch to the 'staging' one:

$ git checkout email
$ git tag old-email-branch
$ git reset --hard staging

You can also rebase the 'staging' branch on the 'email' branch. But the result will contains the modification of the two branches.