Automatically clean merged branches in a project

clean_branches.sh

#!/usr/bin/env sh

delete_type="-d"

if [ "$1" = "-D" ];then    
   delete_type="-D"
fi

current="$(git rev-parse --abbrev-ref HEAD)"

git branch --merged "$current"| grep -v "$current" | while read -r branch;
do    
    git branch "$delete_type" "${branch}"
done

Save this as git-clean-branches somewhere in your $PATH

you can then clean your brances by simply running

git clean-branches