[git] How to remove a branch locally?

By your tags, I'm assuming your using Github. Why not create some branch protection rules for your master branch? That way even if you do try to push to master, it will reject it.

1) Go to the 'Settings' tab of your repo on Github.

2) Click on 'Branches' on the left side-menu.

3) Click 'Add rule'

4) Enter 'master' for a branch pattern.

5) Check off 'Require pull request reviews before merging'

I would also recommend doing the same for your dev branch.