Delete your working branch after it's merged, and pull the default branch

delete-merged-branch.sh

#!/usr/bin/env bash

DEFAULT_BRANCH="master"
CURRENT_BRANCH=$(git branch --show-current)

if git checkout "$DEFAULT_BRANCH"
then
    git pull
    if ! git branch -d "$CURRENT_BRANCH"
    then
        printf 'Delete anyway? (y/n)? '
        read -r answer
        if [ "$answer" != "${answer#[Yy]}" ]
        then
            git branch -D "$CURRENT_BRANCH"
        fi
    fi
fi