Based in a branch, all the branches that already merged in it is passive to be archived.

archive_branches.sh

#!/usr/bin/env bash

current_branch=$(git rev-parse --abbrev-ref HEAD)
target_branch=$1
if [ -z "$target_branch" ] 
then
	target_branch=$current_branch
fi

response="DECIDE"
while ! [[ $response =~ ^([yY])$ ]];
do
    read -p "Do you want to run this script based in branch $target_branch? [Y|N] " response   
    echo
    if [[ $response =~ ^([yY])$ ]]
    then
        echo "Ok, proceeding"
    elif [[ $response =~ ^([nN])$ ]]
    then
    	echo "No, terminating"
        exit 0
    fi
done


branches=$(git branch -r --merged | grep -v HEAD | grep -v master | grep -v develop | grep -v "release_*")
branch_amount=$(echo "$branches" | wc -l)

echo "$branch_amount branches to archive"
while read branch; do
	BRANCH=${branch##*/}

	response_branch="DECIDE"
	while ! [[ $response_branch =~ ^([yY])$|^([nN])$ ]];
	do
		read -p "Do you want to archive branch $BRANCH ? [Y|N] " response_branch </dev/tty
		if [[ $response_branch =~ ^([yY])$ ]]
		then
			echo "Ok, proceeding"
			echo "======= Checking out to $BRANCH ======="

			git checkout -b $BRANCH

			echo "======= pulling branch ======="

			git pull origin $BRANCH

			echo "======= Tagging branch to archive ======="

			git tag archive/$BRANCH $BRANCH

			echo "======= Removing branch $BRANCH ======="

			git checkout $target_branch
			git branch -d $BRANCH
			git push origin :$BRANCH
		elif [[ $response_branch =~ ^([nN])$ ]]
    	then
    		echo "Skipping branch $BRANCH ..."
	    fi
	done
	
done <<< "$branches"

echo "======= Pushing tags ======="
git push --tags

echo "END OF SCRIPT"