If you want to rebase your fork with upstream, first rebase your master branch with:

```bash
git checkout master
git remote add upstream https://github.com/mojombo/semver.org
git pull --rebase upstream master
```

Then rebase your branch to your own master with:

```bash
git checkout pt-BR
git rebase master
```

Then just, check if the things gone right, force a push and you got it!

```bash
git push --force
```

If you're not familiar with rebase, read the [ProGit Book rebasing section](http://git-scm.com/book/en/Git-Branching-Rebasing), it will help you.