Clean up merged git branches in a project directory (use show_clean function first to see what will be removed)

clean_merged

function clean_merged() {
    if [[ -z $1 ]]
    then
        BRANCH=master
    else
        BRANCH="$1"
    fi
    git branch --merged "${BRANCH}" | grep -Ev "${BRANCH}|master" | xargs -n 1 git branch -d
}