Trivial Description
The `dev/checkout_zeppelin_pr.sh` script is useful for locally checking out PR commits.
Currently, it fetches the PR and checks out a new branch.
However, if the script is run while already on the target branch, the updates are not reflected because `git checkout` does not move the `HEAD` when the current branch is already checked out.
To improve the script, it could be useful to allow updates when the current branch is already checked out, ensuring that changes could be reflected in the target branch.